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MG MGB Technical - NCT (MOT) failures
| Dear all,
Took my 81 reg MGB GT in for its test this morning and it failed on 2 issues. 1. Front suspension imbalance, which I assume is caused by a faulty lever arm damper - disapointing because I replaced them both just over a year ago. Anyone know of any other possible cause, replacing these is a difficult job that I would like to avoid if possible? 2. Emmissions (again). This time the CO is at 1.3 %, well within the limit of 4.5%, but the HC comes in at 1627ppm (limit is 1000). Any ideas on how to correct this? I am tuning carbs using a balancer and a Color tune as I dont have a gas analyser. I would get one of the gunson gas testers, but not sure if that would help with HC emmissions - anyone have any experience here? My biggest problem is that hardly any garages seem to have gas analyser equipment these days, so I am tuning as well as I can myself and then putting it in for the test not really knowing what to expect. On the brighter side, recent work I did on the brakes has resulted in good readings in that regard. Grateful for any advice or suggestions Stephen Elster (Ireland) |
| SJ Elster |
| I suppose the obvious question is, what do they mean by ‘imbalance’? It’s a bit vague. |
| Dave O'Neill 2 |
| 1. Haven't heard of this one before. Could it be that it's lower on one side than the other? Potential solution switch springs over. If it's a shocker not damping properly (does it bounce excessively?), you may get away with topping it up with fluid. In extremis, even motor oil (that's what I've got in mine, but it does put pressure on seals). If you do this bounce car a couple of times before refitting filler plug to get air out.
2. As to HC, I'm guessing the SUs at best aren't brilliant in that respect. In absence of better suggestion maybe you could weaken mixture for test? Before that though, make sure plugs and points clean and gapped correctly,ignition timing correct and clean air filters fitted. I remember my late Dad in his Rover 414SLi used to pour injector cleaner into the tank a few miles in advance of the test. Maybe that might help. Hopefully an expert will be along soon............... |
| Peter Allen |
| More info on the imbalance, not exactly sure what the numbers mean. Front axle nearside 67mm Front axle offside 130mm Front imbalance 48% (fail) Rear axle nearside 45mm Rear axle offside 51mm Rear imbalance 12% (pass) I can tell by bouncing the car at the corners that the front offside is softer and spongier. It also makes a slight clicking noise which is new and probably indicates a failed damper? |
| SJ Elster |
| Rebuilt dampers can fail prematurely, but I've only had one like that 30 years with the roadster and 24 with the V8.
Do the bounce test at each corner and that will show any imbalance. Damper fluid leakage is usually the first indication of problems, dampness is only an advisory in the UK, and as far as I'm aware they don't test function anyway - at last not when I've been assisting. If it's dripping it's definitely on the way out. But valve faults could cause incorrect damping with no leakage. Bad luck on emissions, I remember your trials and tribulations last time. High HC means incomplete combustion, which could be down to a multitude of causes. I'm wondering whether an excessively rich mixture could limit combustion to cause a high HC but a low CO, it's not something I've come across. Plug condition? Age? Do a spark test by seeing how far it will jump. I managed to get the roadster tested properly at the last MOT and it came out at 8.82 and 947. The V8 has always been tested and just after I had it it failed at 7.48 and 2365 which was concerning, but simple adjustment got it down to 3.0 and 652. Occasionally if I've been a bit too enthusiastic 'turning it down' it's been it's been 0.36 and 31. On the couple of occasions it has failed there doesn't seem to be any correlation between CO and HC before and after. Do yours try and get it to pass by adjusting the carbs themselves? If they do and they didn't succeed then there is a definite fault somewhere. The Gunsons Gastester is OK for CO, I've had mine for years, but it does have some quirks. If it sits on hot tarmac it reads higher than if I stand it on a saw horse or stool. More recently when level I can't get it low enough to read 2.0 in air, but if I tilt it one way or the other I can! When I can get it to 2.0 in air, or when higher and I subtract the excess from the exhaust gas reading, it is pretty close to MOT results. As you say no help with high HC though. |
| paulh4 |
| Steven,
does the imbalance perhaps relate to ride height? To check just measure from centre of wheel hub to underside of wheel arch and compare one side of the car to the other. Personally I've never thought the Colour tunes to be a good idea, too subjective and you have to allow for modern fuels - not that I know much about tuning though. If possibly it'd be best to have the car fully warmed just before the actual test is done, some garages would suggest you took the car for a run just before the test. Also give the car a good full blow-out run the day before the test and then don't drive to the test station a short distance on choke again get the car fully warmed and if possible another blow-out run. |
| Nigel Atkins |
| Those figures mean nothing to me apart from guessing, like how high the rebound is, ask them exactly what it means. Making a noise could be valve problems. Possibly fixable if you know what you are looking for, but maybe not worth the effort. Numbers that small have to relate to distance from a datum point rather than absolute ride height.
With replacement dampers I always go to my local place so I can check them on the counter - moving them through their full travel, and more importantly positioning them in the middle of their travel and waggling the arms up and down to see if there is a dead zone with no damping which there shouldn't be. |
| paulh4 |
| I was just about to ask what the tester said the figures meant (bear in mind this is Ireland MoT). The imbalance may not be caused by the dampers, what about springs and other items(?). |
| Nigel Atkins |
| Springs set static ride height, dampers have no effect on that unless they are seized. Unmatched springs (as well as dampers) could affect damping but not ride height if the mismatch only changes the stiffness and not the arch, checkable by swapping between sides. Clicking could be from anywhere in the suspension and steering that side, a mechanics stethoscope should track it down. |
| paulh4 |
| More info for those of us not in Ireland.
National Car Test (NCT) Compulsory car testing was introduced in Ireland in 2000 as part of an EU Directive that makes car testing compulsory in all member states. It is an offence to drive a car without displaying a National Car Testing Service disc, if the car is liable for testing. FRONT AXLE SUSPENSION PERFORMANCE Method of Testing Drive the front wheels of the vehicle into the suspension performance tester and operate as per manufacturer’s instructions. (REASONS FOR FAILURE – More than 30% imbalance between L/H and R/H suspension). https://www.ncts.ie/media/1024/nct_manual_july_2018.pdf Before anyone got off on an EU rant, and I'm sure Stephen would agree, before the EU got involved the previous Irish tests were very loose. Looks like I am wrong with just ride height if a machine is involved rather than just an eye and tape measure. |
| Nigel Atkins |
| ETA: Paul, I wasn't tieing in dampers with ride height, I was throwing in other items and possibly their combined effects on each other and overall. Also an assumption has been made because the dampers are new, the assumption may be correct by I'm sure you know what assume breaks down to. :) |
| Nigel Atkins |
| Found out a bit more about the suspension numbers. They are Maha meters rather than millimeters, although there is possibly some equivalence. Maha are the manufacturers of the testing equipment used, and they have implemented their own units for measuring shock absorption. Nobody seems to know exactly how it works but the car is driven onto the testing machine, something happens and the numbers appear on a screen. My guess is that the machine vibrates in some manner and the movement at the axle is measured.
Re the emmissions, the testers can only test and they do not carry out any repairs or adjustments. This is different from the UK MOT, where a garage doing the test can also do the repair work. NCT testing is carried out in dedicated centres that have all the diagnostic equipment and no facility for anything else. Nigel is absolutely correct in that before the NCT was introduced, things were a bit lax here. The insurance companies usually requested some kind of roadworthiness report but there was no standardisation. |
| SJ Elster |
| I don't think damper performance measurement can be required by the EU or we would have it here. Sounds like 'gold plating', usually we are pretty good at that. We have test-only centres as well, usually operated by local councils, which shouldn't be any different from anywhere else. Never been to one so I don't know what their policy is on carb adjustment. It's not been charged for on the couple of times mine has needed adjustment, so not really a 'repair', maybe that was just down to the attitude of the tester. The same goes for headlamp adjustment - if they can do it simply from the back as on my ZS they do and pass it, noting they they had done so, as when a headlamp bulb failed and I had replaced it, even though in theory it shouldn't have needed it. Being under the headlamp ring on an MGB would probably be a fail as they are not permitted to 'dismantle' anything.
The UK MOT on dampers only has four potential defects of which only one relates specifically to the damper performance: (a) (i) insecurely attached to chassis or axle - Major (ii) missing or likely to become detached - Dangerous (b) A shock absorber damaged to the extent that it does not function or showing signs of severe leakage - Major (c) A shock absorber bush excessively worn - Major I question the use of the term 'shock absorber' though. I know many places use that term for dampers, but to me the spring absorbs the shock of going over a bump or pothole, and the damper damps the reaction to that shock. But there we are. |
| paulh4 |
| Sounds like the type of testing we should have over 'ere.
Perhaps it's Ireland and not "the EU" that makes the local requirements - "an EU Directive that makes car testing compulsory in all member states" that is not the same as only one standard of EU testing. Based on how lax Ireland was previously it would have been easier for them to introduce a new system and the equipment required. Many garages are dodgy enough let alone letting them 'fail' a vehicle then 'repair' it and pass it. The fail on headlight aim here I understand is a favourite to keep to expected statistics, I've seen it twice on my wife's previous modern car when I'm convinced it would have passed if I'd been viewing the test. The 'fails' could also make up for the 'passes' given to mates' vehicles that 'pass' from sitting just sitting nearby to testing bays. |
| Nigel Atkins |
| Stephen,
for UK a few have tried Stevson Motors for refurb of LA dampers and reported back favourably on returned unit (but not short, medium or long term running report). Some even restore some themselves, clean, new gasket, refill with fresh oil. For some they find it very worthwhile to get from Peter Cadwell (who used to post on the BBS) in USA and not bother returning their old unit and paying the extra "core charge". Obviously with items on brakes and suspension you're best to do both sides at once. Stevson Motors in UK - http://www.stevsonmotors.co.uk/Dampers.html Peter Cadwell's in USA - http://www.nosimport.com/Lever-shocks-remanufactured/mg-b-lever-shocks The new and especially refurbed units from the usual suspects still seem to be of unreliable quality and possibly not long lasting function. |
| Nigel Atkins |
| Peter, yesterday I saw an 'L' reg Rover 214i in good condition just about to go on to a trunk dual-carriageway, took me back decades, don't see many of those on the road now. |
| Nigel Atkins |
| "Sounds like the type of testing we should have over 'ere. " You jest of course. |
| paulh4 |
| No, stricter testing wouldn't be a bad thing with present day attitudes to vehicle maintenance and drivers expecting a warning light for all faults and issues on the car, to ignore anyway.
Many people seem to drive differently nowadays with a lot less deference to different driving conditions expecting the car to do the thinking for them so any faults are put under greater potential road-testing, no taking it easy when something wobbles a bit, or any knocking noises, as the car is going in for its bi-annual engine oil change in 6 months, the tyres had above legal minimum last time the garage checked two years ago so no need to worry about the very wet roads, anyway the car has ABS (and yes I do know about ABS). "More than 30% imbalance between L/H and R/H suspension" seems a very reasonable figure to me. |
| Nigel Atkins |
| "More than 30% imbalance between L/H and R/H suspension" seems a very reasonable figure to me. The problem is how does the home mechanic decipher what's required to remedy the fault, short of buying new everything? This reminds me of the sort of thing in the EU Procurement Directive that I had the misfortune to have to work with when in gainful employment. I'm pretty sure Steven's car would pass a UK MoT (and in two years not have to worry about it at all). |
| Peter Allen |
| "The problem is how does the home mechanic decipher what's required to remedy the fault" - the same way as all other problems/issues/faults - visual check, physical tests and diagnostics.
There's no difference in front suspension imbalance to emissions in that both are from a machine test and both need the cause of the fault tracking down. Stephen has put the machine measures shock absorption so he would start with damper and spring and associated items and fixings. The mention of the letters U and E together seem to have had there usual effect of logic flying out of the window. :) |
| Nigel Atkins |
| If, as Stephen said in his second post, the front offside has the biggest number, is softer and spongier, and makes a clicking noise when bounced, then the remedy would seem to be to change that damper. Going on about the EU is pointless. |
| paulh4 |
| I'm very surprised at you Paul - yes the clicking sound is liking be from the damper given the the bounce test but it still needs confirming it could also be from another item loose or broken. I'm sure with your electrical and other testing you'd do other conformation actions or tests - or with the damper just look, listen and feel - or test off the car.
Not all comments about the EU - or dare I put Brexit, there I've done it - are to be taken 100% seriously as with a lot of things there is a spectrum of humour, appreciated or deserved of appreciation or not. Once again it seems piss-poor refurb (or new?) LA damper has struck and at 48% difference to the other side it was good that it was picked up at this statutory test as generally things like this get worse and never better. |
| Nigel Atkins |
| "but it still needs confirming it could also be from another item loose or broken. " Which is what I suggested several posts ago. |
| paulh4 |
| Evening Gents-
Stephen With your suspension dilemma, The suspension figures come from a shock absorber testing machine and the figures are related to how far the suspension moves with a given test shake. The truckies around here hate the transport guys that sit the trucks on their shaker and shake them to pieces trying to find worn bushes and things-- to me it sounds like that offside front shocky has an issue and with that fixed up the rear specs will come closer together as well To have an extra 60mm(roughly)travel on the tester means the shocker has an area there that it's not doing anything This could be a faulty shocker (possible) or something loose/worn To get that much travel from something loose it would have to be the bolts holding the shocker to the body, nothing else would effect it that much, so check the mounting bolts and if there's nothing there ,replace the shock. With the HC reading, A high HC is caused by incomplete combustion- This can be a mixture problem, balance, ign. timing , spark plugs, valve clearances, or if you're real unlucky dead camshaft/valve problem So the process would be make sure valve clearances, ign timing and carb balance are right--go a heat range hotter on the spark plugs(just to get through the test) and set them a tiddle wider like .030" Richen it up a litte bit to get it round 3%-3.5%CO Just richen it till your colour tune starts to go orange and then slowly lean it till the orange just dissapears to blue and i reckon your ppm will drop right down Are they measureing NOX willy Ahhh--- just a thought- what carburettors are on your car willy |
| William Revit |
| Check the air filters are clean too, or replace them! As for the dampers,(yes dampers!!), are they both topped up, ideally unloaded.? But could be worn bushes, loose bolts anything which gives rise to lost motion. Unfortunately there are so many shoddy, so called reconditioned, units about you could finish up with the same fault. Paul's advice is good if you can actually examine the unit(s) before you buy, especially for "lost motion" which indicates mechanical wear. |
| Allan Reeling |
| The quality of (most) reconditioned dampers is woeful. I first had the need to buy some for a midget in the early eighties, and they were bad even then. Bearing in mind that the core units weren't actually that old, at the time. In more recent times, I've managed to find NOS fronts for Midgets and I have some NOS rears for the B. I've also had the rears on my B rebuilt by Stevsons. Fortunately, my fronts have been fine. So, yes, beware of poor re-CONs. |
| Dave O'Neill 2 |
| Thanks to everyone, and apologies for inadvertantly starting another Brexit debate!
I will get the front wheel off and have a good look at the suspect damper over the weekend. When I replaced the pair last year I found one was really not working and the other seemed ok, so I might fill that one with fresh fluid and put it back on. Hoping the whole lot will come apart without a hacksaw this time. Re the emissions, I have ordered a gunsons gasmeter and a new timing light (old one was stolen), and will go through the mechanics, timing, carb tuning cycle, then put it in for a retest. One issue is that I have a 582 engine, not the original one, and a 45d4 distributor, which could be original. This is an odd combination and I am not sure whether to set timing as per the engine spec or the distributor. Actually not sure of the vintage of the head, therefore valves,is either so all a bit hit and miss. Will let you know how this works out, Stephen |
| SJ Elster |
| These days with very different fuels to originally timing is normally set for minimal or zero pinking even if everything is matched and with no wear, as the original figures are no longer relevant and you may have to retard from them anyway. With older and mismatched components it can be even worse. I know you have to meet the figures for the age of the car rather than the age of the engine as in the UK, which makes things even worse for you, and the carb type is likely to have more of an effect on emissions than timing. Nevertheless small adjustments in timing could make the difference.
You said earlier that your testing stations only do testing, do workshops have emissions test kit? One would hope so otherwise if a car was taken in for remedial work after failing emissions it might have to keep going back and fore until it passes. If workshops can measure it as well then maybe you could take it there and set it up to pass, then take it to the test station. |
| paulh4 |
| Low CO & high HC = weak mixture in 9 out ten cases. |
| Chris at Octarine Services |
| It seems odd to me, but very few workshops here have emissions testing equipment. They seem to rely on cars throwing error codes to diagnose problems, and that appears to work most of the time for midern cars. I am very much hoping that Chris is correct and that I can enrichen the mixture a bit and reduce HC while still keeping CO within limits. |
| SJ Elster |
| That's a pity, any chance of taking it over the border to a test station to have a fiddle? Or once it fails can you not drive it other than to a booked MOT or workshop?
As far as CO vs HC goes as mentioned above the V8 has always been tested and just after I had it it failed at 7.48 and 2365 which was concerning, but simple adjustment got it down to 3.0 and 652. Occasionally I've been a bit too enthusiastic 'turning it down' prior to the MOT and it was 0.36 and 31, at one test and 0.2 and 190 at another. When it has failed with high CO there doesn't seem to be any correlation between CO and HC before and after. |
| paulh4 |
| Brief update. Discovered that the recon damper was well and truly not working, although it was ok when I put it on just over a year ago. I still had the two I took off last year,one of which was definitely not usable and the other one seemed fine. I swapped the old good one (refilled with fresh fluid) for the newish bad one and it is much better, at least as far as I can tell without proper testing equipment. I am cautiously optimistic that it will pass the suspension test now.
Good idea re travelling over the border to an MOT station that does repairs, but will try a few other things first - the nearest one is about 100 miles from me. Because of the age of the car they only test emissions for CO and HC. Pity in a way as the lamda and NOX readings might be useful to know. I will have a CO gas tester and timing light sometime next week and will get down to some tuning then. Before changing anything I will do a CO test so I can compare it to the official reading from the test. |
| SJ Elster |
| Stephen,
sorry to hear about the recon damper but not all surprised, which is why I offered the two hyperlinks in an earlier post. A note of caution on refilling the previous one with oil, IIRC you don't fully fill with oil, allow space and get air out. Oil- Peter Caldwell of World Wide Auto Parts (USA) who used to post on here and is very well respected for his better than new exchange service on LA dampers cautions about using thick oil too, 30w max. "Stick with the 20W oil recommended (AW68 spec). At most use 30W (AW ISO 100) Best are synthetics like Silkolene or Redline suspension oils. They hold up under heat waaaaay better than standard hydraulic oils.... and these shocks get hot." (AW I think means anti wear, AW68 would be AW ISO 68.) ETA: - I remembered right (for once) from Peter again on loil level - "Of course you can't see how much to add as you are filling the air reservoir. Unlike a differential or transmission, the oil should NOT be at the level at the threads, but a half inch below, which you can't see. So, just add some, if you must. The danger of overfilling is you will cause a future leak by displacing the air space necessary for the expansion of hot oil and force the oil out of the shaft packings. The only reason you would want to add or top up the oil is if you are certain oil has leaked from the shock. Oil otherwise does not get consumed. Adding oil thusly is only a remedial repair." |
| Nigel Atkins |
| Stephen
You're laughing if they're not testing NOX as usually if you pull the ppm reading back NOX goes up Chris is quite right saying 9/10 high ppm readings is because of lean mixture and at 1.3% CO your car is way too lean A good stable idle mixture should be around 13-1 mixture which is 4.0 CO your 1.3 is 14-1, the idle will vary all over the place at that depending on temperature I'd be aiming for somewhere between 3--3.5 CO You're lucky they're not testing NOX as the mixture has to be 14.7 (0.1 co) to get a good reading and to get that you need air pumps or very retarded timing with more throttle at idle to get airflow-----which I find all bull s&*^% as the same amount of fuel is going through just more air to get the right exhaust reading, it really is stupid I'd forget all about NOX and lambda, the MGB engine is too,,old school in design to ever meet the specs for that anyway And the carburettor question, what's on your car, as there are traps willy |
| William Revit |
| Carbs are HIF, professionaly reconditioned less than 3 years ago, so optimistic that they are sound and properly adjustable. Will replace spark plugs, check timing and aim for 3 to 4% CO. |
| SJ Elster |
| Topping-up dampers on-car requires a different approach between front and rear. The fronts are easy as the filler is on the side so you just fill until it runs out, and you have plenty of air-space above. The rears have the filler on top so you have to be careful not to reach the bottom of the threads, and with a torch/flashlight I've always been able to see that on my cars. Filling fronts off car need similar care as the usual method would be to have them lying down.
Lambda and NOX - don't go looking for trouble, life is difficult enough for you as it is! Even if they did measure it for you there is no reference source available that I'm aware of to compare it with for an engine/car the age of yours. In they UK they only record Lambda on cars first used after 1st August 1992. |
| paulh4 |
| Stephen
Thanks for the info on the carbs Now, because they are HIF carbs, 4% might be getting a little too close to their (testers) 4.5% limit--I'd stay back at around 3.5% max The issue with HIF carbs (well not really an issue)is that the jet tube is attached to a bi-metal strip which slightly richens/leans the mixture depending on fuel temperature. The idea of this is to keep the idle more reliable over a larger temp range than earlier SU carbs could If you set the co at 4% with the engine at normal warm operating temp there is a slight chance that when you get to the testers and if the car has been sitting a bit then started up the flow of cool fuel from the tank could just be enough to put you over 4.5 for a while till the heat soak gets back into the fuel bowls At 3.5% you should be safe ------------- Just out of interest and for your own knowledge--NOX is the nasty shi@ and the only way to eliminate it is a properly working cat. converter and it has to be at exactly stoich-14.7:1....This is why later cars have O2 sensors to keep the mixture at that while the engine is going Earlier fuel injection systems used to run at this for normal driving but idle mixture was a bit richer and also most systems went to a leaner cruise mixture, both preventing the cat to operate properly The latest requirements are that the new cars have to meet the no NOX reading right from startup, even from a cold start and stay that way under all load conditions It's been like this for a few years in parts of the US but now it's everywhere Unfortunately all the older cars without cats and on unleaded fuel, drive around all day spewing out NOX everywhere and they wonder why so many people get cancer now Personally i think we were a whole lot better off getting doses of lead than this lot willy |
| William Revit |
| Thanks all for valuable advice. Will aim for 3.5% CO and hope that fixes the HC problem. From everything above it looks like this stands a good chance of working as long as valves, ignition etc are in good order. Stephen |
| SJ Elster |
| Very intersting graph in this article https://www.crypton.co.za/Tto%20know/Emissions/exhaust%20emissions.html showing relationships of emissions gasses varying with fuel/air ratio. Not sure how accurate the scale is but it shows the patterns nicely. |
| SJ Elster |
| Not a bad writeup but they confuse things a bit with the co-o2 relationship You have to remember too that they are trying to get to the magical 14.7 so that the converter works properly to kill NOX where you don't have that to worry about so you can tune to suit the specs you have to meet Have fun willy and don't forget, if you have cold plugs in it the readings will improve quite a bit with warmer plugs |
| William Revit |
| There is nothing magical about the 14.7 mixture - the graph bears out that max power tends to be produced nearer to 14 - indeed I have found that the ideal CO setting for the B series engine is around 5.0, it gives clean pick up, smooth idle and best peak power, probably due to the cooling effect on the incoming charge of the excess fuel.
Additionally, the NOX and HC readings are markedly lower with a slightly rich mixture compared with the 14.7. Now my old girls no longer require an MOT or emissions test I run them at 5.0 - before, I used to detune them to pass the test and retune them after .... |
| Chris at Octarine Services |
| I am in complete agreement with Chris, on this I always set my carbs to run at 5% CO, and as said the HC reading is lower than when set to a lower percentage, at this reading I get a good pick up no flat spots, a smooth 750 RMP idle and well over 30mpg, |
| Andy Tilney |
| I agree as well, we all know these engines go there best with a nice healthy amount of fuel going through them around 12:1 (5-5.5co)on full load but we're not talking performance here, we're trying to get through the emissions test
Chris, you mention, (There is nothing magical about the 14.7 mixture )---not quite right 14.7 is the only mixture ratio that a cat works correctly at to eliminate NOx, anything other than that and it just doesn't work 100% 14.7 is way too lean for any MGB on full load and that's exactly why the cars fitted with cats have to have air injection into the exhaust to weaken the exhaust entering the cat to meet the 14.7 required at the cat to make it work as designed As mentioned before it's all bullshi@ to pass the emissions laws of the day willy |
| William Revit |
| Willy i say there is nothing magical simply because it is the mixture required for the cat - which our cars do not have - the magic comes in having the mixture "right" for the engine spec ;-) |
| Chris at Octarine Services |
| Gunsons gastester arrived so I did a CO reading without changing anything. It came out as 2.4%, wich is 1.1% higher than the official test. I wasnt expecting to get a complete agreement but this is further out than I imagined. I did it a second time, having left the machine in fresh air and calibrated it again and got the same result. I am going to tune for 4.5% on the gunsons in the hope that that will equate to 3.5% at the test centre. Is that a reasonable approach??? I will also use the piston lifting technique and hope to find some correlation between that and the gastester.
Stephen |
| SJ Elster |
| I would pop off the suction chambers and remove the pistons/needles and using the tip of a finger to feel the level of the jets, wind them up until they are level with the bridge. Then wind them down two full turns of the adjusting screws. This will give you a starting point and you will know the jets are equal. Gas test and it should be close to 5 - wind the jets up by a quarter turn each and retest until you get the result you want. |
| Chris at Octarine Services |
| All good but don't forget to have the engine at a nice warm operating temp to set it up as it will alter a tiddle with temperature being HIFs
Chris' advice on equalling the jets to start with is good advice and then when making adjustments from that point do both carbs equally--lifting the pistons is ok for a guide but better off having both jets equal I agree with what you're saying Chris,there was never any doubt-- just trying to give Stephen a background so he can get his head around what he's up to and what he needs to do and what he doesn't have to bother with Cheers willy |
| William Revit |
| As well as adjusting both jets by the same amount make sure it is in the same direction. The same goes for the idle screws or you will upset the balance. But that is only after you have got the mixtures and flow the same on both carbs.
Both jets equal as Chris describes is the initial starting point, but if by 'piston lifting technique' Stephen means the lifting pins then that is for fine tuning. After two full turns down from level then independent adjustment for the highest idle speed, further independent adjustment is made to get the same response from the lifting pins. In theory both cars should end up with the same number of turns from being two full turns down, but some differences are inevitable. If you find you are having to adjust one carb significantly more than the other to get the same highest idle, or response to lifting pins, then a problem with one or other carb, or pair of cylinders, is indicated. Only when you have both carbs responding to the lifting pins the same do you connect the CO meter on a single-exhaust system, and it's then both that carbs must be adjusted by the same amount in the same direction to get the required CO reading. |
| paulh4 |
| Thanks again all for useful advice. I checked the timing and reset the carbs as per the advice given. Got them nicely balanced, both showing 6 units on the flow meter and responding as they should be to the lifting pins (first time I have got that to work properly). Connected up the gas meter as per instructions, it takes about 20 minutes to settle and calibrate, and the reading from the exhaust is showing as 4.3%. The reading goes up and down a bit though, no matter how long you leave it to settle. Given that my first reading on the gasmeter was 1.1% higher than the official test, I am going to leave it as it is and go for a retest tomorrow.
I still have a slight inconsistency in the exhaust note, a kind of irregular burble - if that is a misfire I could still be in trouble with HC readings. I have checled all plug leads with the strobe and they are fine so really not sure what is causing this. Retest fee is v reasonable at 27.50 euro, so probably the cheapest way to get it checked properly. Will post again tomorrow, Stephen |
| SJ Elster |
| Back fron the retest, and still have a fail on emissions.
CO 2.75% HC 1761 ppm This compares to a gunson reading of 4.3% CO. What to do next??? 1. Enrichen mixture a bit more and hope that lowers the HC? Disapointing that the changes made so far have had no impact on HC at all. 2. Try to track down the slight misfire? Could be an ignition problem so will start there. 3. Make another attempt to find a garage with proper testing equipment? Might have to go across the border to Northern Ireland for that. 4. Retard the timing a bit?. Currently set to 9° at 1000 rpm. I beleive retarding can reduce emissions but I dont know how much to change it. Grateful for any further thoughts on this, Stephen |
| SJ Elster |
| Can't say I'm surprised based on my experiences with emissions tests over 24 years, and what you said about exhaust note. I can't see it being anything simple like tweaking mixture or timing, there almost certainly has to be a specific defect somewhere.
It's probably incomplete combustion, a misfire may have you richening the mixture to get to a CO reading and that is causing the high HC, but that's only one of many possibilities. As said way back what is your plug condition like i.e. colour after a decent run - assuming you can still do a decent run of course which I assume you can given your comment about going over the border. Secondly short out each plug lead in the cap in turn and note how much the revs drop. There will always be some variation between cylinders, and I know opinions vary but if one makes no difference then that's the one I'd be looking at. Compression test? Dry and wet, hot engine, all plugs out, throttle wedged open. Timing jitter? Missing flashes on one or more plugs? If you get an erratic exhaust note at idle you should be able to see a corresponding missing flash, if that's the problem. Confirm the timing pointer and pulley are correct by removing plugs 2 to 4, and turning the engine by hand until you can feel an increased resistance from No.1 on its compression stroke. Remove that plug as well and look through the plug hole as you continue to turn the engine. Judge where piston rise it at its highest i.e. has stopped just before it starts to go back down again, you may have to go back and fore a bit to be happy you have the highest point, then look where the pulley notch is in relation to the timing marks. It should be right under the last pointer it passes, which should be the biggest one, which is TDC. |
| paulh4 |
| Stephen, re the misfire, have you put any new parts on since last year's last statutory test, like spark plugs, HT leads, dissy cap, rotor arm. or any other new parts? I think you put te misfire is constant rather than intermittent, does it change when the car is fully warmed up and under load? |
| Nigel Atkins |
| In response to Paul's questions above
1. Spark plugs look ok to my eye, will attach a picture 2. Confirmed tdc lines up with the pulley marks 3. Tried shorting out each plug in turn. No teal difference between them, but perhaps no. 3 made less of a difference. 4. Tested the ignition for missing sparks using the timing light, all looked ok. 5. As above using 4 inline testers, again all looked good to me. But not claiming to be expert. 6. Will do a compression test when I can get hold of the equipment. BUT compression was tested as part of the head/valve work carried out about a yeae ago. 7. Checked for timing jitter using the timing light. It looked ok to me but I dont have snything to compare it to. I also tried disconnecting the brake servo in case it was leaking and upsetting things, but it made no difference to the exhaust note so put it back again. I have only changed spark plugs since last year, when it scraped past with a temporary retardation of timing. This is the same misfire I have been trying to track down for over 2 years now, and nothing has made any difference. I even had the head cleaned and got the valves reground but it is just the same as it was.  |
| SJ Elster |
| PS Also swapped the coil for an unused one I had on the shelf. That also made no difference to the misfire:). What I am calling a misfire is a kind od burbling noise, a bit like blrbbbbb blrbbbbbb blrb br blurbbbbb... at idle. It all evens out at higher revs and I wouldnt worry about except for the suspicion that it is causing my HC problem. Stephen |
| SJ Elster |
| When you disconnected the servo hose, did you plug it if you removed the hose from the servo, or plugged the port if you removed the hose from the inlet manifold?
Those plugs look a little odd to me - very even, but I'm surprised to see the insulator as white as that with the body as black as it is. Mine don't usually have as much contrast as that i.e. a browner insulator and a less black body, but that could be down camera and monitor. Two of mine attached, Look pretty close in the photo to me. Yours look like Champion, what number? Clutching at straws now, but have you tried different brands of plug? Some do say that their car does run better with one brand over another. Failing that, I think a second opinion over the border is needed.  |
| paulh4 |
| Hi Paul, I disconnected the servo hose from the manifold and plugged it using a piece of tube and a spark plug. It seemed like a pretty solid seal.
Plugs are Champion RN9YC, gapped at 0.9mm as they came. I see what you mean about the colour. They are only a few days old which might explain the white insulator, but black round the edge is odd. Could that be oil, implying head gasket problems? I dont have any other symptoms such as water in the oil or overheating though. I guess it might be worth trying NKG plugs, to see if that makes any difference. Or is the gap on mine too large? Haynes says 0.89 mm for the 45d distributor and .61 to .66 mm for the 25d. I have the 45d but an engine that would have originally been fitted with a 25d. I figured I would leave it at the larger number to match the distributor, particularly since I have the optronic electronic ignition, but that might not be best. One more thing I might try is setting the timing at maximum centrifugal advance as per John Twist approach. Would have find the correct figure (32° possibly?) and work out what to do re vacuum advance. This would really just be an experiment to see if it cures the misfire, what do you think? Stephen |
| SJ Elster |
| Blocking the hose with a plug is fine, we had to that with a pal's V8 (remote servo) when the servo kept sticking and jamming has brakes on. In Ireland, as it happened, on a tour from Dublin to Galway and the west coast.
Could be the engine hadn't run long enough or hard enough to get a stable plug colour if they are that new. Something else that has been mentioned by one or two is that resistor plugs have caused problems compared to non-resistor type, another reason to try a different make. I'd stay with the larger gap on a 45D4, it's possible the smaller gap on the 25D4 was guarding against HT breakdown on that distributor as the bigger the gap the higher the voltage goes before the plug fires. Nevertheless it's another thing to try if you can get enough time on the emissions tester. Blanking off vacuum advance is another possibility, the factory had to do that on an individual basis with cars for North America if it was the only way they would pass the tests there. Remember John Twist is talking about low-compression engines, the timing considerations for those can be quite different. I'd be more inclined to vary the timing at idle and see how that affects the exhaust beat. |
| paulh4 |
| - ETA: Paul posted whilst I was typing and we are agreeing on your plug colour and method and resistor plugs, we don't always agree, even though Paul is a lot more knowledgeable than me but I have decades of using various classics as daily use, work, holidays, commuting when they're old cars (called classics to push the selling prices up). -
I was thinking the same as Paul with perhaps trying NGK plugs instead. And agree your plugs look a little odd with black against such white but I'm not sure how much your plugs say as it depends on when you removed them, engine fully warmed, blow out drive, instant turn engine turn off plugs pulled, etc.. If you've got electronic ignition and the rest of the ignition system is in good condition and working well then plug gaps can be wider. But as an example for you, my Midget has a fully electronic (123) dissy (bottom as well as top) and some say you can have the plug gap on mine at 0.76mm or even 0.89mm when the book setting is 0.64mm. On Peter Burgess's rolling road he found my car ran best with the (NGK) plug gap at 0.71mm. And I find gaps tend to widen with use but not always all equally (not that I good at setting gaps). Peter is an expert on tuning B-series engines you could ask him if he's able to recommend a gap to try, obviously without your car in front of him to see what's what and on the rollers nothing can be exactly certain. BTW the 123, the makers, of my fully electronic dissy told me not to use resistor plugs and Peter said they were unneeded so I stopped using them, and saved a few pence. As you've already found DIY testing equipment is not always the most strictly built and calibrated so tends to get you in the ballpark rather than the exact spot so should be treated as such. |
| Nigel Atkins |
| Will see if I can get some non-resistor plugs. Are the ngk ones bp6es? |
| SJ Elster |
| Yes. The bp6e will also work but to be sure still with bp6es. https://www.sparkplugs.com/Data/uploads/Charts/NGK_Plug_Chart_1.jpg |
| Nigel Atkins |
| Resistor plugs aren't _needed_ for our cars, they are designed for modern cars to eliminate interference to their ECUs. NGK for example used to state "In nearly all cases - apart from some very old low output ignition systems - resistor spark plugs can be used in place of the non resistor versions." but I can't see that now, or anything similar for Bosch or Champion!
Fuel is another factor in combustion, what brand and grade are you using? Said pal with V8 lived in Ireland at the time and one day rang me saying his engine was making a terrible noise. He held his mobile phone in various places but the sound quality just wasn't good enough for me to say if what I was hearing was good or bad. He'd recently filled up in the middle of nowhere from a no-name place and wondered if he had contaminated fuel. Eventually he put some fresh stuff in from a town filling station and all was well. |
| paulh4 |
| Cant find any plugs around here that dont have an R in the name. Moss have some Bp6es so will pick some up next time I am over.
I did find a garage with a Sun emissions tester and they hooked it up and let me play with carbs and timing, all for a very reasonable 20 euro. However, nothing I could do would bring the HC within limits, so it looks as though I really do have a problem. Their suggestion was to add some oil stabiliser to slow down any oil coming past the piston rings and put it in for another test. I guess there is nothing much to lose by giving that a go and see what happens? I use the best petrol I can get, usuallt from Circle K, but it rated at 95 octane, and that is all there is here now. Anyone any experience of the octane boosting additives on offer? All the best, Stephen Elster |
| SJ Elster |
| See below, seem a little expensive but I don't know exchange rates, tax and delivery differences. You could go to eBay for cheaper but I prefer fresh stock for these sort of items.
I was dealing with octane boosters the other day, can't remember the results now though so will come back with that, I do remember a test years ago that found all but one booster didn't add power and one made things worse. Paul would know which years of B went better with which octanes, or look on his website, my '73 GT was fussy for more octane. http://www.lawnmowerspares.ie/spark-plugs/ngk-spark-plug/bp6es.html https://www.bikeworld.ie/ngk-spark-plug-bp6es |
| Nigel Atkins |
| IIRC(?) this is the FBHVC recommended octane booster -
VSPe Power Plus. But you might want this for quicker effect at the moment - Petrol Power EcoMax One Shot Boost. MGOC do Classic Castrol Valvemaster. Here's a claimed octane booster that seems to get a good review from a couple of reasonable sources - Lucas Oil 10026 Octane Booster Review. You have to buy these products by the box load for regular filling up of petrol though so it gets expensive. Rather than octane boost as such regular cleaning additives to the petrol might help you, we can get them over here already in the higher octane petrol. Thing is you might have to burn through some petrol with (or added to) additives to get the cleaning effects. I used to use STP® COMPLETE FUEL SYSTEM CLEANER-PETROL but I don't really know how good it was, one bottle every 4,000 miles now but less expensive than octane boosters and the combined booster, once you have your system clean you just keep it clean. https://www.millersoils-shop.co.uk/vspe-power-plus https://classicvalvemaster.co.uk/products http://altrabiofuels.com/lucas-oil-10026-pk12-octane-booster/ http://www.stp.eu/en/products/fuel-additives/complete-fuel-system-cleaner-petrol |
| Nigel Atkins |
| Now I don't like the idea of needing to add anything to your engine oil but perhaps just to get passed this test this time, well(?). Engine oil is a favourite topic of mine, not that I am technical (in anything) so questions should you chose to answer them. What oil do you use - brand, model, weight? Do you have an oil cooler thermostat fitted? What length of journey or runs do you make in your MGB - miles/time? Do you normally bimble or drive in a spirited manner? |
| Nigel Atkins |
| Stephen sorry I dropped a hyperlink, to Petrol Power EcoMax One Shot Boost. It might be good to use for your test then perhaps use another product as a regular cleaner.
Saw STP® ULTRA 5-IN-1 PETROL SYSTEM CLEANER which might be better than their other cleaner for you for regular use. I've no idea how effective either are but I used the other as it was easy for me to get in the local shop (used to say every 6 (or 12?) years ago IIRC. It says - Increases octane rating of fuel by up to 3 numbers. Improved combustion and engine cleanliness drastically reduces emissions of hydrocarbon (HC), carbon dioxide (CO2 ) and nitrous oxi Ideal for use as a pre-MOT test clean-up treatment If it does as it claims then you could also alter the engine timing and carb mixture to get you through the test (as well as perhaps a fully warmed engine and engine oil) that hasn't cooled too much from waiting for the test. http://www.millersoils.co.uk/products/0/106 |
| Nigel Atkins |
| 0.9mm plug gap is too wide ----------0.7mm is the go And get rid of the resistor plugs the combo of resistor plugs and big gaps like that are too much for the poor old coil at the best of times |
| William Revit |
| Not sure what an octane booster would do in this case, its purpose is to make spontaneous combustion harder, can't see a logical fit there with excessive unburnt fuel. Mid 70s do seem to need higher octane, my 73 would only just run book advance on 4-star, slightly less on unleaded even with 99, to control pinking. An MG run up Shelsley Walsh some years ago was notable for how many cars of that era were clattering away like billy-oh on the hill, including mine, whereas early and later were not. Additives will claim all sorts of things, but again it's cheap enough to be worth a try. Don't mix them though trying to find what works best, this was advised against when lead replacement additives first came out as they can react with each other and cause valve and seat problems.
Looks like you would have to go over the border for one of the big names, but it seems the whole of the island of Ireland only has 95. 0.9mm or 35 thou was the standard value for 45D4 distributors for decades. Been using that on the V8 for 24 years probably most of it with resistor plugs. But as said before using a non-resistor plug has benefited others in individual cases, and closing the gap is easy to try. There is definitely something wrong somewhere, and while tweaking round the edges may let it just scrape through (as it seems it did last time) which would at least let you use it for a year it's only a sticking plaster and you are likely to have the same problem every year while the root cause remains. If you can borrow a pair I'd try a different pair of carbs, ideally HS. Might need a bit of jiggery-pokery with fuel supply and cables, and it's getting desperate. Have you tried contacting the MG Enthusiasts Club Ireland? http://www.mgireland.com/ |
| paulh4 |
| Stephen,
my posts on petrol additive boosters, not unusual for me, got a bit convoluted and mixed up so to summarize - . for a one off shot to help you get through this annual test you could use Millers EcoMax One Shot Boost (250ml bottle treats 60 litre of petrol) . then for regular use go on to Millers VSPe Power Plus for octane improvement, ethanol protection (and lead replacement if you need it), endorsed by the FBHVC, 500ml bottle treats 500 litres so about 6p per petrol litre. Millers Petrol Power EcoMax One Shot Boost - 250ml - https://www.millersoils-shop.co.uk/petrol-power-ecomax-one-shot-boost Millers VSPe Power Plus Multishot - 500ml - https://www.millersoils-shop.co.uk/vspe-power-plus-multishot |
| Nigel Atkins |
| I put my last post before seeing Paul's.
I think a combination of the Millers Petrol Power EcoMax One Shot Boost to mainly clean, with the lead and octane boost, the change of plugs and gap, and with adjusting the timing and carbs it should add up to a difference at least. If this gets the car through the test then perhaps the the use of a 500ml bottle of Millers VSPe Power Plus Multishot for two or three tankfuls should give enough time, mileage and use to check again to see how successful this is. Hopefully the misfire might also have gone. I've picked the Millers as it's endorsed by the FBHVC and as you know I use Millers oils so have some confidence in the (UK) company but I've no idea how good the petrol treatments are but at 6p/litre I might give it a go as a test it's a lot less than the difference between 95 octane and Tesco 99 or others and see if it's as good as Tesco 99 for cleaning and performance. |
| Nigel Atkins |
| With regard to spark plug gap and no disrespect Paul but IIRC you've not had your car on the rollers (recently?) so you don't have seperate confirmation whether the gap is at it's best or whether it could be improved on with a different setting - not that I know, you could be running at optimum gap already.
I can promise you that Peter offers excellent value with the use and tuning on his rollers and gives excellent (and unlike some, realistic) results and I'm sure you'd like his no-thrills (what-so-ever) engineering premises. |
| Nigel Atkins |
| Never had either of mine on rollers. I'm going by 24 years of emissions testing on the V8, the issue here is not squeezing out the last ounce of performance but passing that test. That includes one where the plugs had inadvertently done 9 years and 25k and the test before that was 3.86 and 186.
Stephen unfortunately has a very significant issue, but much of what is being discussed here is only tinkering around the edges. Something else occurred to me and that is to look closer at the ignition with LT tests. I'd be measuring the resistance of the coil and ballast, as well as voltage at the coil +ve and -ve and coil current, both static and running, with an analogue meter. Looking back I see you have Optronic, so static tests may not be possible. In which case I'd see if I could retrofit points and a condenser to eliminate weak output. Incidentally some time back it was said that with electronic ignition you can run a bigger gap, but that only applies with something like capacitive-discharge systems which output a much higher voltage. As far as I'm aware the usual names mentioned these days are all inductive-discharge which are basically the same as points i.e. they are simply a switch that turns coil current on and off at appropriate times, albeit a transistor switch. As such they actually deliver LESS current through the coil than a good set of points, which is why the factory used a low-resistance coil with the initial 45DE electronic system which like points is a fixed-dwell system, and a very low resistance coil with the 45DM4 system which is variable dwell. |
| paulh4 |
| Stephen,
suddenly thought - your 1981 reg car, it is a UK model and not a re-import or anything unusual, had other changes made or emissions stuff added or removed? Paul, not thinking of wring out the last drop of performance, and certainly not power with a Midget or BGT unless well under expected, just thinking of good or very good running performance for engine and other component health and mpg for the longer journeys (the Midget tank holds less than 26 litres, wonder soon have more pee stops than fuel stops, it's cheaper). For all settings on the cars they will be individual to the vehicle to some extent so a wider or narrower spark plug gap may help this particular car and its systems. If there's a big problem all that's been mentioned may be tinkering around the edges or it might be that by doing a standard run through of cleaning and setting up it does the job or discovers the fault, be it large or small. By passing the test the car can be run which will probably help in finding the issues and see if the car gets better or worse with each stage of rectification, meters, standard and DIY test figures are all well and good but the aim is to have the car running well - or very well. :) |
| Nigel Atkins |
| If your idle mixture is ok then I'd think the carbs, seeing they have been reco'd are ok
I'd fit a 'new' set of NGK BP6es plugs or even BP5es to get through the test I've had Champions here that are dodgey right out of the box, I realise the plugs you have are made in France and ours come from who knows where ,but' Have you measured the resistance of your plug leads and coil lead and the cleanliness of the contacts where they fit in the cap Just on the off chance, the carbon button in the centre of the cap that runs on the rotor button--------is it there or gone missing-? Where does the engine breather go on your car If it's direct to the carbs ,has your car got the correct sealed oil filler cap and are the breather hoses hooked up correctly There's something not right here somewhere willy |
| William Revit |
| And the ign. points There were some dodgey sets here a while back that deteriorated as soon as they saw daylight The contacts were only plated instead of being solid and died very early causing a rolly idle a bit like a very lean mixture does might be worth having a look at yours and see what the contacts are doing |
| William Revit |
| Optronic fitted |
| paulh4 |
| Interesting point about the breather hoses. I have checked these for leaks, and they seem ok, but I have read that a blockage in the air filter at the front of the head can cause problems. Anyone know how I could check for this?
As far as I know, the oil filler cap should be vented on my set up - the breather hoses are attached to the carbs but I dont have any US reg polution controls. Will check the ignition LT and HT again, but my suspicion is that something is putting oil into the combustion chambers, either because the engine is worn or because it is being sucked or forced in somehow. Will also try new plugs and smaller plug gaps. Keep the ideas coming in, they are very welcome and likely to throw up something I may have missed. Stephen |
| SJ Elster |
| Willy, oh, no! Not oil sucking! :) |
| Nigel Atkins |
| Stephen,
I’m not sure what you mean and want to check by air filter/blockage/at front, but you can check the breathing by taking the oil filler cap off whilst the engine is running (when warmed) and you should hear a slight difference, confirmed when putting the oil filler cap back on. Or just remove the oil filler cap and put the palm of you hand over the oil filler, er port/tube/filler neck and dis connect the breather hoses from the carbs and blow down the short hoes and you should feel it on your palm. You could also check the carb ports are clear. For the oil filler cap, if you have one of the bling chrome type they’re not as good at breathing as the standard plastic oil filler cap with bigger vents and mesh filter inside. You can clean these caps if you want (see photo) or just buy a new one. I’ve always found these cars appreciate regularly cleaned or replaced carb air filters and regular thorough engine oil and filter changes (drain hot, for as long as possible, same for g/box and rear axle). I’ll have a look I think John Twist shows checking the engine breathing before setting carbs in a vid of his. A good hi-res (well as much as you can get loaded) photo of the engine bay may highlight something to those that know especially if your engine varies from standard. I can’t remember if you have a copy of the relevant Driver’s Handbook to refer to or not (this is not a Haynes or factory Workshop Manual).  |
| Nigel Atkins |
| Have a look at the start (or all of this) JT vid - https://www.youtube.com/watch?v=4nvGLgO6pj0 |
| Nigel Atkins |
| Stephen Does your car have a carbon canister connected to the rear of the rocker cover |
| William Revit |
| Whilst a faulty oil filler cap that is letting too much air through will result in a weak mixture, a blocked one won't cause anything like this problem, and it would be more apparent with CO than HC.
But Stephen - you do remind me of something! There are two passages in the carb flange which must pass through to the air filter or it upsets the mixture and hence emissions. There should be a gasket there, and original gaskets (left in the attached) had to go the right way up to line up with the holes. Later gaskets (right) are 'idiot proof' in that they can go either way up ... but idiots can still get the air filter base the wrong way round (guess how I know ...) May not be the case with yours as it's a problem with HC and not CO, but worth checking. As far as burning oil goes you need to do a compression check as suggested way back. It would also impact on how many miles you do to the pint, of course, and is normally visible as a blue cloud when blipping the throttle after idling for some time, or opening the throttle after a long down-hill on a trailing throttle. Checking the resistance of all the HT leads as per Willy is also worth while, very high resistance leads can result in weak sparking and possibly incomplete combustion. Around 10k per lead is typical, but double that shouldn't cause a problem.  |
| paulh4 |
| Stephen,
Paul might have covered what you meant by blocked air filter with the gasket holes but this would apply to both of the carbs and filters to check not just front. This is also covered in that JT vid that I posted a link too. I wasn't suggesting an oily filler cap mesh would be the cause of your problem(s), emissions and possibly separate misfire, just that a combination of small issues can contribute by themselves or overall. Checking and if required cleaning or replacing would be general servicing and maintenance anyway. Whilst many problems can be intricate and require more than the usual tools and/or knowledge to sort them a great deal of problems and issues are sorted by just general servicing and maintenance which often just boils down to cleaning and lubing, if it didn't I wouldn't be able to do it and my Midget would never move. Your problem's will also involve setting up and tuning but this is always best done after the basics of servicing and maintenance - which you may have already done. This of course doesn't allow for mistakes made previously like gaskets upside down - I done it once by being impatient, but I don't feel too bad about it as many times in the past I paid a lot of money to professionals, including "specialist experts" that have made mistakes, balls-ups and often just poor quality or shoddy work. I now normally have an idiot who is very reluctant to work on the car and get his hands dirty - but at least he's good looking, charming and modest and very cheap so I put up with his attitude, mistakes. That's of course without considering all of the piss-poorly made modern parts, never assume because it's new that it won't be faulty or even the correct part even if it does work. Also consider that an 81 reg BGT in Ireland may not be the same as an 81 reg in UK, I don't know if it was the case back then but later at least some Jap grey UK imports went through Ireland, I know as my mate had a selection of Mazda Eunos he could chose from back in the 90s. |
| Nigel Atkins |
| Dear all,
Several questions have been raised that I have not responded to yet, so here goes. Car is a 1981 UK model, subsequently imported into Ireland. Mainly oroginal but the engine is an 18v582 from an earlier model. Carbs and distributor match 1981 specs. I will upload a picture of the carbs and breathers I can blow through the crankcase breather and feel air at the filler as per John Twist video, so I think that is ok. I am aware of the holes in the carb to manifold gasket. I did get these the wrong way round once but they are correct now. I do not have a carbon cannister of any kind. Plug lead resistances are all between 4.5 and 10k, resistance proportional to length, which seems ok. Carbon button in dizzy is fine, and I checked the resistance from there to the coil end of the coil HT Lead at 10.2k, which also seems ok. Havent done compression test yet Am about to look for problems in ignition LT circuit. Will also check valve clearances, although this was done fairly recently. Stephen  |
| SJ Elster |
| I've turned photo to save necks. Well you seem very much on the ball, so well out of my level, I expect you have to have the later dissy and carbs on the earlier engine for Ireland regs and/or costs of replacements(?). The only things I notice from the photo are (not at all useful) - . the proud Leyland badge . how stringy the later engine bay appearance got . unless that's the colour it is, a new petrol filter for xmas perhaps So over to those that know more (not difficult I know).  |
| Nigel Atkins |
| Thanks for turning the picture round. That is the colour of the filter element, but I will replace it anyway as it is a couple of years old. |
| SJ Elster |
| Have just discovered that my valve clearances are too small. They seem to be about 0.006 inches. My guess is that they were set at 0.15 mm instead of 0.015 inches. This was done as part of the valve stem seals and head cleaning work by a professional mechanic who charged over 800 euro for the job. I dont think I will be going back there! Will reset them and see if that makes any difference Stephen |
| SJ Elster |
| Stephen,
well done on finding this. I might be telling granny how to suck eggs or stating the bleeding obvious but if you're resetting the tappets then you'll need to check and adjust the rest of the chain - (tappets), (points), (plugs), mixture in that order. I'm surprised I didn't put it before as that's what I usually suggest, going through service set ups, the Driver's Handbook and stress the start of the JT vid as he always stresses the four points (one of which doesn't really apply to UK). I got distracted from my normal well worn path of favourite suggestions, I make these because it's all I know and because as I put going through basic service and maintenance checks often finds issues or the issue and it's all that's need. I hope it is the case this time as if the first setting is out the rest will be to try to counteract this. I wish I could say I'm surprised that such a simple mistake could be made by a professional but as I've put I've had it many, many, many times. Plus like some posters they usually don't like to double check things or consult books and certainly not the Driver's Handbook that gives (standard) settings. A problem is when you only drive your own classic you have little point of reference to how well it performs compared to other similar models that are in good mechanical condition (and used often). Let us know how you get on, try the new plugs on smaller gap too, you can alter them and the following links in the chain if required. |
| Nigel Atkins |
| Ah Same old story again All the basics have to be right first Lucky you haven't burn a valve or two with them like that Now In your pic there's a hose(shiney black) that appears to go from near the oil cap and out the left side of the pic----Where is that coming from / going to |
| William Revit |
| Blimey, 'skin' and 'rice-pudding' come to mind, never mind tappet rattle. Given that, absolutely anything could have been done incorrectly! But, step by step. |
| paulh4 |
| Willy, I wondered about that and then thought - oil cooler pipe(?), very shiny though. Sod's Law the time I don't do my usual limited mantras and it would have helped, tut. |
| Nigel Atkins |
| That shiny black hose is about where the oil cooler hose would be - not normally that shiny though unless covered in oil ... Another question is the smaller pipe that comes off the back of the inlet manifold. That would normally be the vacuum advance pipe, but it would usually go straight over the rocker cover to the distributor, not come in front of the oil filler. It looks like it could also have lots of tape wrapped round it. |
| paulh4 |
| Good spot. Photo res was too low to tell much but my reading of it was that it's the vacuum advance pipe with a bit of sleeving but tbh honest I didn't notice the tape wrapping. Pipe, hose and cable routing can be individual to different owners, factory routing wasn't always the best anyway, I always look at it as UK cars are factory converted to RHD. |
| Nigel Atkins |
| The shiny pipe is the oil cooler. It isnt wet, just unusually shiny. The small tube is the vacuum advance. It takes the scenic route to the distributor. Everyone is of course correct about starting at the start will try to learn this ledsm. Again. |
| SJ Elster |
| Starting at the start is one of my sayings, to be told "it won't be there", "wasting time checking that/those", "the problem is not from that".
Another - RtFM (read the manual) and have you checked the bleeding obvious yet, or how many times. When my mate was taking youngsters to train and they'd been to electronics training, he'd test them by giving them something to repair, I suggested taking the fuse out of the power lead. They all played with the tools on the appliance but not one thought to test the the wall socket, power supply cable, plug or fuse because they'd been taught to think higher, it was sexier to play with fancy tools and they didn't have the experience to start at the basic foundations before moving on to the fun bits. Having put all that I've no idea what ledsm means unless it's just a typo. |
| Nigel Atkins |
| Ledsm is lesson. Will learn to type one day |
| SJ Elster |
| I thought it might but as with the cars it not good to assume, as my wife often tells me. I struggle to get through typing a word let alone sentence or paragraph, I think just about every post I make has at least one typo and often many and all my edits often add to the mistakes. |
| Nigel Atkins |
Maybe typing ledsms Nigel--lol Just a bit off subject --sort of But down this end of the world our feeler gauges are marked differently for imperial / metric All imperial sizes start with a decimal point as in----- .015" but metric starts with a zero------ 0.15mm Makes it simple, and hard to mix up I guess it would be the same there, so the engine man has made a big boo boo |
| William Revit |
| Willy, cigar to you, just looked back and in your first post here you suggested checking the tappet chain, I thought it'd been mentioned, next you'll be promoting the Driver's Handbook. :) My wife says that I'm actually a pretty fast (one-finger) typer, however accuracy is a different matter. I think the feeler gauges are marked the same here but don't have a lot of experience of such tools. |
| Nigel Atkins |
| Impressed that your wife praises your typing I get growled at for doing the one finger without having my arm supported, I usually end up having to support my wrist with the other hand to stop my shoulder getting sore and then get growled at for that It's just a wife thing----all good fun Cheers |
| William Revit |
| Yes I was surprised she said my typing was quite fast as she does work training on computers with staff that could be our grandchildren and that they're slow with a keyboard. |
| Nigel Atkins |
| Further update in this long running saga.
Reset the valve clearances to .015 inches, went through the whole timimg, carb balance and mixture setting again. Replaced the fuel filter and carried out as many checks on the ignition as I know how to. Car is running really nicely, I think better than at any time since I have owned it. I still have the exhaust burble though, so still concerned about unburnt petrol in the emissions. Did a compression test and got the following readings: Dry, 159, 166, 153, 157 Wet, 159, 169, 169, 170 Any thoughts on this - they dont look too bad to me, although obviously not perfect? I am going to have an official retest and see what I get there. I might just hace done enough to get it through, time will tell. Just for good measure I slapped in the recommended fuel and oil additives, on the basis that it might help and shouldnt do any harm. Will report back after the retest, Stephen |
| SJ Elster |
| Meant to add that I got some NGK BP6ES plugs and set gaps to .025 inches, which is actually recommended in the Optronic documentation, Stephen |
| SJ Elster |
| Stephen, you'll need to run the petrol through to get the additives cleaning and taking the car out on runs before the retest will also have the car cleaning itself through. If you're really lucky doing this might even reduce or get rid of your burble (if you're lucky). The compression test results I'll leave to the others as I don't know, but I've a feeling you may need to do them again. And I was going to ask about the spark plugs but it's covered. Good luck. |
| Nigel Atkins |
| Just thought, to complete the set, did you change the paper air filters (or recently at a service)? |
| Nigel Atkins |
| Because of MGB's having a slightly sporty camshaft grind they never idle completely smooth so I wouldn't get too pumped about that, but it is a bit difficult to rate a burble from the other side of the world-
The wet compression test on an MG is a bit hit and miss if you haven't done it before-- The pistons have a dish in the middle and if the oil goes straight in on top of the piston it just sits there like a dry test and doesn't do anything to seal rings etc Given that your tune has been out of whack etc really your numbers aren't bad, a decent run will work wonders If you go to do them again, it's plugs out,get 2 pistons down to bdc. and give your oilcan one good squirt through the plughole as flat as you can to hit the other side of the bore, let it sit for a min. then the oil can run down around the rings Turn the engine half a turn to get the other 2 down and repeat Don't forget to remove the primary wires from one side of your coil to prevent any stray sparks from starting a fire or giving someone a boot--Doing this will also prevent the risk of sending your coil or rotor button to the bin. With the rolly idle, there is always the possibility that it may have a camshaft on the way out or because the engine is an unknown quantity maybe it has a sporty cam in it----? willy |
| William Revit |
| Low-comp pistons seem to have a dish but Stephen's should be a high-comp engine and mine at least has flat-topped pistons.
WSM says 170 at 275 rpm. To me cylinders almost the same dry and wet indicates problems. Normally the wet test causes the rings to seal better, so when it makes no difference and the figures are low as with No.1 the implication is a burnt valve, which could be causing the burble. No.2 is reasonable dry, but again not much difference between dry and wet, so again possibly a slight valve leak. And as said before with previous gaps as small as 0.15mm i.e. 6 thou that could well have done the damage. 3 and 4 with a low dry and a noticeably better wet indicate to me that there is a problem with the rings sealing, so could be burning oil and causing the high HC. But how you adjust the valves can make a significant difference to compression readings. 'Rule of Nine' is the usual method, but I and other have found that at the strict RON point the clearance is still changing, so I adjust mine at the point of widest gap. Why this should be I don't know (other than knackered cam) as in theory the whole of the back of the lobe i.e more than 180 degrees of rotation of the cam should give a constant clearance. There is also the question of how much oil is put in, and whether that is all at the same time, or just before each wet test. Also the tests must be done on a hot engine, all plugs out, throttle wedged wide open. |
| paulh4 |
| I was thinking perhaps the wet test at least might not have been conducted to spec, otherwise perhaps given the previous valve clearances the engine might not be performing at its best but if Stephen has nothing to make the comparison how is he or us to know.
I've seen lots of classic cars which are not as well running as they should be because owners have never really driven them, and not frequently enough, so have no real idea how well they should or could perform and accept and promote the idea that these old cars need to be nursed along at bimbling pace, particularly very shiny show-type classics. |
| Nigel Atkins |
| All std MGB pistons have a dish in them L comp pistons more so than H comp but they are all dished and need the oil pointed at the bore while the piston is down the bore to get good results from a wet comp. test other wise the oil just sits in the dish and does -0 |
| William Revit |
| In view of recent comments, I suspect I didnt put enough oil in for the wet test. I did each cylinder in turn and took the readings as soon as the oil went in. I will do it again, using slightly more oil and let it settle for a while before cranking the engine.
Engine was warm with all plugs removed but I didnt have the throttle wedged open. Looks like I need to do this all again to get usable results. If the rings are not sealing that would mean a major engine rebuild or replacement. I dont have time or cash for that at the moment, so it would have to go into long term project mode. Stephen |
| SJ Elster |
| It's true I only looked at pictures of my engine with the head off and didn't see any dishing, but it's also true that a wet test added more than 20, just by squirting oil in from a can. Maybe I was just lucky in hitting the bore with the oil.
Another test is leak down, or at least injecting compressed air into each plug hole in turn with the piston on it compression or expansion stroke i.e. both valves closed. You will get some hissing from the oil filler but shouldn't get any from the carbs or exhaust. I diagnosed (just injecting, no leak-down tester) a faulty exhaust valve that way and it proved to be the case with the head off. If you move the piston through its stroke and the hissing in the oil filler changes significantly that could indicate bore damage. A proper leak down test will quantify that. |
| paulh4 |
| I did the comp tests again, with throttle wide open and taking more care on the wet tests. Dry 158, 166, 166, 155 Wet 172,173,173,162 As begore these are not perfect but they are all within the 10% range. The middle 2 cylinders seem to be better than the outside 2. Any thoughts on these numbers? Am booked in for official retest on Wednesday. Stephen |
| SJ Elster |
| Stephen,
before Wednesday get in as many runs of at least 20-30 miles as you can, longer is better, and if you can get a few good blow-out, Italian tune-up, runs then all the better. This will help the whole car, not just the engine, anyway but will also get the cleaner through the fuel system and perhaps the oil additive fully working. I'd go for a nice long run, or runs, in the early hours when the traffic is less and when bursts of higher speeds and higher revs can be used safely. Although some classic owners may not believe it it isn't illegal to use the classic in the dark and even in the wet, the car will not instantly turn into a pumpkin or pile of soggy rust. |
| Nigel Atkins |
| No problems with those at all. I did wonder about the variation in the previous readings given how consistent the four plugs were. If the ignition LT tests mentioned 15th Oct are as they should be, what does that leave? Some fuelling problem? |
| paulh4 |
| One thing to be considered is that the engine is from a 72 model, so it is going to struggle to get down to 81 model emissions standards. I do believe it is possible if everything was in perfect condition, but in the real world....
On the positive side, it is driving really well and petrol consumption looks good. Havent done enough miles to measure it properly, but have done 120 miles since last fill and the gauge is reading higher than it often would after that distance. Will see how the test turns out. All I am intending to do before then is the recommended driving to get everything warmed up and cleaned out. Will post again on Wednesday, Stephen |
| SJ Elster |
| You are right it is, but you have the later HIF carbs, and the engines themselves really aren't that different.
Having set my 73 up purely with the lifting pins for 30 years as it hasn't needed to pass emissions, this year out of interest I got them to test it and it came out at 8.82 CO and 947 HC. This regularly gets 35+ mpg and long-distance touring in France over several tankfuls got over 40. I suppose I could weaken mine down to 3.5 and have it retested to see what the HC is, but by the same token you could enrich yours so it fails CO, just to see what happens to the HC. If HC just creeps inside the limit with CO several points out, then that's obviously not the problem. But if HC comes way down when CO is only just too high ... that needs more thought. The easiest way of doing that if you can take it somewhere that will do continuous monitoring is to pull the choke a fraction at a time and see what happens. If you do alter the carbs, make sure you adjust both by the same amount in the same direction, counting the quarter-turns so you can put them back to how they are now. This must be really frustrating when it's running well, but either you keep trying different things to see what happens, or give up. |
| paulh4 |
| Thanks, Paul. Even more frustrating is that I only need to get it through this test and it will be exempt by the time the next one would be due.
Will keep trying different things, it all adds to the learning process. I could always take it off the road for a year and start driving it again when it becomes exempt (40 years after first reg) but that is a bit like giving up, and I want to do the Gordon Bennet runs next year - 3 days of runs over a bank holiday weekend, all based fairly close to where I live. More news soon... |
| SJ Elster |
| Stephen,
I still think you want to give the car more runs before the retest. The idea is not just to pass the test but to get the whole car, not just engine and dampers, running well so that you can use its full performance (which might be mpg too). This will also help you prepare for Gordon Bennet type runs, you need the car running well consistently well before the event otherwise it could lead to perpetuating the stereotype of classics breaking down when actually used. Have you changed the paper air filters? |
| Nigel Atkins |
| Good point about the air filters. I put the current ones on about 2 years ago, only a few thousand miles but no harm in changing them. They look very clean though, and I wont be able to get new ones before the next test - I have to get most parts delivered from UK or collect them when I come over. I will be working tomorrow but will do a decent drive on Wednesday morning before the test, Stephen |
| SJ Elster |
| The paper Mann(?) ones used to be so cheap I'd change them every 6-months. It's surprising how much dirt, dust and debris an engine can pick up even when stationary, bonnet down, inside a garage or out. the filters can look clean until you compare with new.
I find these engines really appreciate clean air filters and regular oil and filter changes. As you've already found regular routine servicing and maintenance is very worthwhile - and on the whole car with the important components like brakes, (tyres), steering, suspension, lights and windows, as you've found the engine will wheeze and puff along regardless of tune. I'd go through the whole servicing schedule and get the whole car performing well, passing the annual test is just a minimum standard it doesn't mean the car is going that well or as it could or should. Course it depends on whether you want the car to ride in a precession or drive in a rally. |
| Nigel Atkins |
| Nigel
Never a truer word has been said--- "Although some classic owners may not believe it it isn't illegal to use the classic in the dark and even in the wet, the car will not instantly turn into a pumpkin or pile of soggy rust. " Take it out and give it hell before the test to blow the sh@t out of it and make sure it's nice and hot for the test This modern fuel with the ethanol in it, which most has now doesn't burn properly unless it's right up to temperature The Targa rally fellas here are running E85 and have a real hassle with it, they sit waiting for their turn at a stage and even though their engines are running they cool out from the fuel and when it's their turn to boogy, it's not till they get a few Ks up the road and they get some heat into them that they start to hook up properly I've done a lot of work on methanol burning Chevs and the difference between running at 200F of 185F on methanol is unbelievable, on a good chev there's around 30 HP difference to be gained there-------but that's on straight methanol Don't know why I through that in there but there you go---Not suggesting for a second that you should run an MG at that temp, just stressing that up to running temp is better with ethanol in the fuel willy |
| William Revit |
| I simply can't see that 5% ethanol and 2 year-old air filters are going to be the cause of this problem, unless the car has been run in extremely dusty conditions for that 2 years. But like other suggestions they are no big deal to change. Going back to the carbs, do you know their history i.e. were they definitely from the original engine? Do they have little alloy tags on them? If so what numbers do they show? |
| paulh4 |
| We don't know if there still is a problem, it might have already been resolved. The air filters and petrol additive and other stuff will help rather than hinder and are to also progress on from the original problem for the car not just to pass this last test but to get it running well for the sake of it and to make it ready for the Gordon Bennett, and before and after.
Stephen has said the car (engine) is going the best since he's owned it which is both good and bad, bad that it hasn't run this well before as obviously it had the potential. And of course the engine and carbs are really among the least important items on a car but improvements with these could encourage improvements to the more important items which will make the whole car run better and be able to take advantage of the engine improvement, simply by service, maintenance and repair. This isn't just about spirited performance driving but also mpg, less wear and tear on parts and components, smoother and better ride and drive overall, ect.. When you have nothing to compare your classic against it's difficult to know how well it is actually performing. A Spridget owning mate drove my Midget and straight away noticed a problem I hadn't because I'd got used to it. There's a strong impression that classic cars are fragile, slow and poor handling and performorming and this is perpetuated by many classic car owners who don't know any better and keep their classics in this condition because they infrequently use them and only bimble about in them so have no real idea of how well they could or should perform or how to get and keep the classic in a condition to perform as it should. A big part of this is proper servicing, maintenance and repairs along with regular use over reasonable length journeys. |
| Nigel Atkins |
| Good luck tomorrow Stephen, fingers crossed for you |
| William Revit |
| Thanks for the encouragement all.
Just coming back to Paul on the carbs. When I got the car just under 3 years ago, the carbs looked fairly rough and I was advised to change them. They had aluminium tags indicating they were of the type used originally and I got reconditioned carbs of the same type as exchange items. Cant remember off hand what the number on the tag was though. At that stage I did not realise the engine was not original, or even from the same year. In the end, I have to admit that I didnt know what I was buying, and still dont know much about the history of the car. Since I have had it I have (with huge help from this group) replaced the clutch slave, most of the brake hydraulics, both front lever arm dampers, the rear bump stops, all of the handbrale levers and the starer motor. I have also bypassed the ballast in the ignition and fixed a badly wired relay that was flattening the battery. As well as paying a mechanic to do a valve job. All in all, far too much investment to give up on now, so will keep going no matter what happens tomorrow. Stephen |
| SJ Elster |
| When you bypassed the ballast did you replace the coil? Or confirm what type it was? Also why did you bypass it? Getting the wrong combination of coil and ballast can cause problems, but I'd expect more emissions problems from using a 12v coil WITH ballast than the other way round. |
| paulh4 |
| Hi Paul, I worked out that the car had a standard 12v coil and was using the ballast resistor. I swapped the coil for one that was designed to run with the ballast. That new coil packed up after a few months so I put the old coil back in and bypased the ballast.
Did another check on vacuum leaks and found that the carb nuts were not as tight as they could be, so tightened them up a bit, probably about half a turn. Will check balance and mixture again in case doing this has changed anything. Spraying the base of the carbs with carb cleaner produced a very slight rise in rpm before tightening nuts, same test afterwards had no effect. It is possible that this small vacuum leak has been causing problems for a while. Annoying that I looked for it earlier in the process but didnt find it. I think that should give me a fighting chance of passing, we will find out later, Stephen |
| SJ Elster |
| OK, swapping a 6v coil with ballast, to a 12v coil without ballast, shouldn't cause a problem in this area. |
| paulh4 |
| It passed!! 1.95% CO, 557 ppm HC. Gunsons was reading at 5.1 so I expected CO to come out around 4 or so. Many thanks to everyone that offered advice and encouragement, this forum is priceless. All the best, Stephen Elster |
| SJ Elster |
| Congratulations. Here's to another year of trouble-free motoring. |
| Dave O'Neill 2 |
| Stephen,
well done! You must feel great. Bears out that these DIY testers and tune-up kit aren't exact so need to taken as such. I'll repeat the advice I always give for a classic you don't know the history of, gained by me at very, very, expensive experience - give the car a (rolling) full 30k-mile mile service and check, whilst at the same time using it over reasonable length journeys all-year round and don't spend your money on any cosmetics or upgrades or improvements (unless the original parts have to be replaced) until you've run the car year-round for 12 months. That's as much as I know so as they say on Dragon's Den, I'm oot. Cheers. |
| Nigel Atkins |
| Excellent - especially as you say it's the last time you will have to go through the rigmarole. Just shows how many apparently small things can add up to cause a problem. |
| paulh4 |
| Paul,
I'm sorry (well not really otherwise I wouldn't post) but see my post of 17 October 2019 at 11:37:51 - >> ... just that a combination of small issues can contribute by themselves or overall.<< I may know bugger all technical but I really do have a lot of personal experience of problems with cars (and some in the car trade). The time to get technical is once you've fully covered the (simple) basics, same with tuning, you can't progress successfully with tuning until the servicing and maintenance work has been fully completed. I'm sure your Bs would be ready for Peter's rollers, perhaps you would be able to keep the mpg at slightly more acceleration. :) I have a strict rule in my Midget to never overtake a single MGB, I always overtake them in pairs. :) |
| Nigel Atkins |
| Good stuff Stephen ---Well done |
| William Revit |
| Until the valve clearance issue and the intake leak I really didn't think any of the tinkering would solve the problem, and it didn't. I made no similar comment for those two as I could imagine they would have an effect, especially the intake leak, as the carb mixture(s) would have to be increased to compensate for that.
What it does show is the need for checking, checking, checking going through all the basics rather than plumping for new bits. I've told you, I have no interest in putting either of my cars on Peter's rollers, I'm quite happy setting-up my cars myself and with how they run, and listening to what they are telling me. The fact that I may get a smidgen more mpg or performance really doesn't interest me, even it were detectable. If I wanted more performance I would buy it, but having driven an F1 and flown a Spitfire nothing will ever come close to the exhilaration they gave me. Except sky-diving perhaps ... |
| paulh4 |
| Paul, you really must learn when your leg is being pulled, I even put smilies to help you this time. Go skydiving I'm sure you would enjoy it. |
| Nigel Atkins |
This thread was discussed between 03/10/2019 and 24/10/2019
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