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MG Midget and Sprite Technical - Hot engine gremlins

Evening all. Apologies for the long post, just want to get as much detail across as I can. Some will have read my thread in the general section about picking up my first midget yesterday. The 300 mile drive home went mostly without incident, but I did have an issue at one stage when I stopped halfway home for fuel.

After 2 hours of problem-free motorway driving I came to a stop and was aware of the engine idling at very low revs, almost at the point of cutting out, though it revved freely when the throttle was pushed.

Thinking nothing of it I switched off and fuelled up, but when I turned the key again the engine struggled to turn over at all, as if either the battery was almost flat or something had seized. It was a similar feeling and sound to when my alternator seized on another car, but the alternator and fan turned freely by hand so I ruled that out.

The strange thing was as I continued to try the starter, sometimes it would struggle to turn the engine as above, sometimes it would spin freely but not engage the flywheel, and sometimes it would just give a loud click and do nothing. I thought this was because I had gradually run down the battery but eventually after 20+ attempts it spun strongly and started fine.

I have read several hot start threads on here and each of the different symptoms listed above seem to point toward a particular cause (for example bad earth points, vapourising fuel, bad starter motor, ignition components etc) and usually it's the same thing happening each time the key is turned, but the randomness of the starting symptoms in my case is odd.

It doesn't seem like vapour lock as the engine never cranks without starting - it just struggles to turn over at all, or the starter doesn't even engage. Even if it takes 20 attempts, on that 20th attempt when the engine does turn over it always starts, as it does when cold or not as hot.

As a novice, this sounds to me more like bad earth points reducing the power from the battery. I'm not sure why it would be worse when hot though? I think the starter needs looked at anyway but that may be a separate issue as it sometimes doesn't catch the first time, no matter what the engine temperature. I will start at the earth points anyway, any other advice would be much appreciated.

Cheers,
Paul.
P Robson 1500

It does sound as though there could be a high resistance somewhere - battery terminals, solenoid terminals, starter body to engine or engine earth strap.

It could also be a dodgy starter motor.

Given the random nature of the symptoms, it could be several different faults.
Dave O'Neill2

Paul,
First, dont assume that it is all one problem!
If your battery was well charged - which it should have been on a mild day and having driven a fair distance. Then I would suspect a poor earth lead (engine to chassis - down next to o/s steering rack mount). If it sometimes spins well, and sometimes doesn't, then the fault could be worn brushes on the starter motor or even a faulty starter solenoid.

Poor hot starting could be a completely different issue - though made more apparent by starter motor problems. Lots of possible causes - fuel vaporisation has been mentioned if the heat shield is missing. But at this time of the year I would doubt that was the cause. I would check points gap first as they do wear themselves out of adjustment. But I would suspect that it may be that it is running rich. Which is why cold start is OK, hot start isn't. Check that the choke control cable is allowing the choke lever to fully return. Check the colour of the plugs for sooty deposits, and maybe raise the jet setting by a couple of flats of the adjusting nuts. Check air filter is clean.

But in truth, unless the choke cable is sticking, then the only way to get it right is to do a full systematic retune, starting with setting the valves, then points, plugs, timing and last of all, the carbs! Follow Nigel's good advice and give the car a full service. Apart from doing it good, it is the best way to learn about the condition and give confidence that it won't let you down!
Guy W

Cheers Guy, a few things to keep me busy at the weekend then. The learning experience has started already as I've never owned a car with carbs or manual choke before - I suspect that may put me in the minority on this site.

I think I'd be more concerned if the engine was turning over but not starting, suggesting a fuel or ignition issue, but the fact that it never fails to start when the engine does turn over gives me hope that it will be a more simple fix. Whether or not the starter motor is the cause of my problems I will be checking it out anyway and replacing if necessary, as I had an old Mitsubishi van which did similar and I was always wondering if it would start when I got in it.
P Robson 1500

Check the earth strap before you spend money on a starter motor!
Incidentally, if you haven't already done so, you can download (or order a paper copy) of the Moss catalogue which has pretty useful parts diagrams. For instruction on setting up SUs refer to Burlen Fuels and look for their technical downloads http://sucarb.co.uk/history-burlen

Guy W

Paul,
don't forget all the advice you got on your other thread

checking electrical connections/wires/leads/earths are clean, secure and protected or making them so is always a good idea, and it starts at the battery going forward

my Midget used to have the occasional kerchung miss with the starter then fire the next turn, I soon tired of the excitement of guessing when it would happen next

IF you need to adjust the CB points then you'll also want to check the plugs, timing and carb mixture - as all this is part of a service you might as well check as part of a service

once you fully service/check the whole car you will have the timing/ignition/carbs set and unless you have worn or faulty parts you shouldn't need to check or adjust them until the next service - you should not need to be constantly fiddling with them

bear in mind as I put before many owners, even long term, have little or no idea, or perhaps care, of how well the whole car should or could operate, go or be driven and may well have accepted their car at well under it's potential (or not bothered) and only carried out an occasional oil change and carb fiddling thinking, or not caring, that all Midget "do that" or "are like that"

even if the car has been well looked after and well used a full and proper 36k-mile service/check-up may be due or some items previous not due or missed
Nigel Atkins

Paul, check the battery connections first, it may have the lead cup type fittings over the battery posts.

Corrosion can build up unseen inside those and can usually be cleaned off easily with a wire brush (there are special brushes shaped to fit inside the positive and negative terminals that can clean them out with a couple of quick twists of the wrist. The pos and neg have different sizes by the way so you shouldn't be able to connect the cables to the wrong posts)

This corrosion often shows up as you have described the problem, basically an intermittent loss of power, if there's corrosion clean the white or green deposit off with hot water. It won't hurt the battery but will leave lots of dilute sulphuric acid around so wash that off with another splash or two. (sulfuric, for our cousins across the seas) ;)

If the terminals pass muster look at the wires on the solenoid and chack that the solenoid is firmly screwed to the bodyshell. Rust under there is common and easily countered with sandpaper or emery cloth. If the solenoid isn't properly earthed at the metal/metal contact area guess what happens?

Yes intermittent starting problems.

These are two of the most likely problems that you can check in minutes before you get the vital servicing started.

Note I said VITAL, servicing is as the chaps have said, essential for efficient running.

And is also very easy to do with any BMC/BL car of the period, follow NIgel's good advice and get the BMC/BL drivers handbook.

Worth its weight in ... paper... and gold
Bill1

I missed a bit out (as usual)
>>my Midget used to have the occasional kerchung miss with the starter then fire the next turn, I soon tired of the excitement of guessing when it would happen next<<
... so I bought a new starter motor but by this time my staggered 36k-mile service/check-up was well in hand and the kerchungs had become slightly less spasmodic

just so you know, the others already do (too often), I loathe doing anything other than driving my Midget, I only carry out regular servicing, maintenance and repairs to keep my Midget at its potential and when I can I pay others to do the work, I get no joy working on my Midget even when it's at my convenience so as you can imagine I have a low tolerance for roadside repairs or breakdowns, I've already had enough of those to know prevention is a lot better than cure

I want my Midget to reliably do what I expect of it without fuss, I'd expect if I'd not driven it for a month during the coldest part of winter (not that that would happen anyway and my car is outside 24/7, 365/6) that, still in the coldest part of winter, I could start it up and drive 100s of miles in it immediately (with just doing the usual driver long journey checks)

driving it regularly for reasonable distance journeys throughout the year also helps to keep the car reliable (and iron out wrinkles quicker) easy for me as my Midget, like others on here, is used as a daily car

sermon over, time for bed
Nigel Atkins

Wow....Paul youve got these guys jumping threw hoops.....theres more info here then in the archives!

Ha ha ha!

Nigel...What work did you pay to have done? Who did you have do it?

I thought MG ownership required the occassional roll up your sleeves from its owner to fix it yourself...

An occassional blood sacrifice must be offered from your knuckes!

Its part of the pleasure of ownership/care and feeding rewards system built into each car!

Lets face it! The MG Gods can be jeolous for your attention!
Steven Devine

Starting - Personally I would replace the starter solenoid anyways, then read the manual and take it from there.

Hot engine - mix a definite suspect - easy to adjust, but do check choke functions OK, chuck the air filter for new, check carb jets are totally clear, and that there are no leaks in the carb pipework/vacuum advance etc first.
Mark O

To me all the stuff in Paul's initial post says "No electrical power getting to the starter" Mark.

quoted: "Thinking nothing of it I switched off and fuelled up, but when I turned the key again the engine struggled to turn over at all, as if either the battery was almost flat or something had seized. It was a similar feeling and sound to when my alternator seized on another car, but the alternator and fan turned freely by hand so I ruled that out.

The strange thing was as I continued to try the starter, sometimes it would struggle to turn the engine as above, sometimes it would spin freely but not engage the flywheel, and sometimes it would just give a loud click and do nothing. I thought this was because I had gradually run down the battery but eventually after 20+ attempts it spun strongly and started fine."

None of that points at ignition system faults, carburation omissions or anything else, even the battery sounds as if it's up to scratch.

Turn key - bugger all happens! - that is BATTERY TO STARTER CIRCUIT alone,which I found very often in nearly thirty years dealing with broken down motor cars in t'AA.

It can be the KEY SWITCH portion of the ignition circuit but the description does not bear that out, the switching function seems to work. Only problem is getting the juice through the wires to the starter.

Hence my suggestion to check the electrical connections first, battery terminals, earth points and solenoid body.

If the solenoid body is not earthing properly the thing just won't drive the starter.
Bill1

I concur!
Dave O'Neill2

Bill has been trained and learnt by experience to start problem solving at the beginning with the basics, without doing this you may not successfully move on further and you might miss the actual cause of the problem that is in the basics

same with tuning any of the car you can't successfully tune any of the car without first having done all the basic servicing, maintenance and repair work

battery or battery related faults are still one of the main reasons for breakdown call outs but usually it not the battery at fault, batteries are very reliable, most owners are not so

I think the starter missing sometimes is a separate problem which won't help with the main problem caused by poor electrical connections/wires/leads/earths after these are sorted hopefully a full and proper service will find, sort and prevent any other starting and running problems
Nigel Atkins

There is an excellent Lucas document called 'Lucas Fault Diagnosis Service Manual' that goes through all the point to point voltage/resistance checks for the starter circuit.

It is downloadable from this link, and many others:

http://www.gomog.com/allmorgan/LucasFault.pdf

It also covers charging, wipers and most things 'Lucas' - very handy reference manual.

Richard
Richard Wale

Well now, I still think that from Pauls' description, there are likely to be two unrelated problems. Bill describes the likely causes of the intermittent starter performance. But then there seems to be a separate difficulty with hot starting.

As I don't think current weather conditions are likely to cause fuel vaporisation and Paul has confirmed that the heat shield is in place, then I still think the likely cause is an over-rich carb. And a likely suspect here is the choke not fully returning. If that is working OK, then a methodical engine tune up is probably the best solution, although a worthwhile stand-alone first adjustment would be to check the points gap.
Guy W

Not wanting to throw a red herring in, I have had two problems in the past with hot starting. One was a DIY imobaliser were the PO had switched the low tension circuit with a switch that had become faulty. lots of head scratching before an auto electrician diagnosed it. The other was a cracked dizzy cap that let moisture in that vaporised and condensed into moisture inside the cap and caused the spark to track. Not saying that either of these could be the cause, but if we're throwing hats in.........
Pete Ottewell

Guy, Paul says in his OP

"It doesn't seem like vapour lock as the engine never cranks without starting - it just struggles to turn over at all, or the starter doesn't even engage"

i.e. as long as the starter actually turns the engine, it starts.
Dave O'Neill2

Thanks Dave, Missed that inference! ;-)
Guy W

all possibilities if not cause or main cause at moment but choke and CB points will be covered by the service, IIRC Paul has said he wants to change HT leads, dissy cap and rotor arm (if required of course)

but PO added/altered electrics are always a delight of the imagination so fair point there, I did note in other thread added front lights so signalled up the potential there

Paul also mentioned that this is the first car he'd with choke, add in never folded the hood and the mystery of the operation of the heater control and you have the newbie's holy trinity for the good book but Paul being a refrigeration engineering is possibly genetically allergic to reading or referring to instruction manuals like the DH (but might look at more technical manuals, graphs, illustrations and tables if impressive enough) :)

I can remember a boss often shouting down the phone to the engineer/technician having problems "RTfM"
Nigel Atkins

Loads of good informative reading here gents, it's all very much appreciated. Frustratingly I have to wait until the weekend to get stuck in but in the meantime I have a chance to do some more reading. I've not been near the car with a spanner yet but already I feel I've learned some useful things about it, maybe not all applying to the issue immediately at hand but no doubt the time will come.

Nigel - I'm not particularly averse to reading manuals, in fact it will be refreshing to read one which isn't a loose translation from Japanese.

You have me on the heating control though - I haven't read up on that black magic yet but it's near the front of the to do list.
P Robson 1500

Paul,
it's all very easy and very informative reading in the Driver's Handbook with only a few minor updates required for the 30+ years difference (which I can give you) - the procedure for refilling the coolant system alone with pay for the book in time and hassle - if you remember to refer to it, not all 1500 owners do remember ;)

if you get the good book and read it and refer to it you'll soon be answering some questions on here from others ! :)
Nigel Atkins

Bill - Your comments are fine, but I would not rule out a dodgy solenoid. Cheap to fix and thus eliminate one possible source of the problem. As for hot starts I guess that needs clarifying whether that is a real problem.
Mark O

I wouldn't be inclined to replace parts as a matter of course, as you could be introducing new faults, particularly with the rather unknown quality of modern parts.
Dave O'Neill2

Whether it is the solenoid or not is easy to check by simply seeing if the problems persist if you start it by shorting across the solenoid terminals. If this cures the problem then it would point the finger at the solenoid itself being the culprit. But even then, as Bill advised, it may just be a matter of cleaning terminals.

Anyway, for all the good advice being banded about, I suspect that Paul will want to investigate and research for himself what needs doing and how to do it on his new acquisition. Finding out for oneself is all a part of the fun and the learning process. One can have too much well intentioned advice!
Guy W

Just to put out a daft question...

Are we doing a repair to get the car operational ? Or are we doing a complete service, clean, and tune up

It seems we have 2 differant camps offering similar advice

Just to add my 2 cents to the on going confusion

Has paul tried grabbing hold of the coil when the engine is warmed and running for 1/2 hour or so

If paul gets a 3rd degree burn on his hand after grabing the coil bare handed...then we have something to look into

Also ... was there any spreodic play / movement in the techometer while driving home

Another thought, check your timing it could be set to advanced, not to mention valve lash is set to thin

God you have to love throwing stuff against the wall like its spaghetti without any plan, diagnoises, or even knowing what you want to accomplish....

So when do we start burning cash, thats almost as much fun as burning books in the streets

Prop
Prop and the Blackhole Midget

Prop stop with the red herrings already

Paul has a problem with the starter circuit ONLY

When the starter works the car starts ;-)

What more confusion do you want to throw into a simple fault?


:-)

Don't you have a room to strip?


A car to drive?
Bill1

Bill

If thats all it is, then most likely the starter just needs pulling and a good washing in acetone... or I hate to say, gasoline and reinstalled DRY with NO lubrication

But I took pauls comment that it was running rough and would not restart after a while from running but the starter just spun the engine slowly and clunky and would eventually start.

Red harring....with chips, MMMmmmMMM good

Prop
Prop and the Blackhole Midget

Update on this...

Since I bought the midget and posted this I've had very little opportunity to use it or investigate the little gremlins that were part of the deal. This starting problem didn't happen again for a while but after a 40 mile drive the other day it happened halfway home. Luckily I was on a hill so it bump started fine, but later that evening at home and again in the morning with a fully charged battery it still just barely turned over and didn't start, so I re-read everyone's advice and went to investigate.

First thing to check was the earth strap, and I quickly discovered that I did't have one. Now I would have assumed that the car would never start without that, but it must have found a route elsewhere, albeit not a very reliable one.

As a temporary measure at least, I connected some earth cable from the starter mounting bolt directly to the battery strap on the bulkhead and the car started strongly and immediately, so hopefully that's all there was to that problem.

My question is though - the cable I ran is 10mm copper earth cable normally used in houses (I use it at work for grounding solar panels to the fuse box). Will this suffice as a more permanent measure or should I add something more heavy duty elsewhere?

Many thanks,
Paul
P Robson 1500

don't know the 1500 personally but all the others have a braided strap underneath from the bellhousing to the RH chassis leg, and sometimes a plastic covered cable between the front engine plate and the body side of the LH engine mount.


David Smith

Thanks for the reply, I have had a good look around everywhere on the engine and there definitely isn't anything like that. No idea why it would be missing, unless it was removed to do a particular job and then forgotten about.
P Robson 1500

not a bad Idea to have a second major earth lead

it could have been that you car was earthing through the choke cable(?) possibly(?), it would get hot so you'd know if you touched it

the earth strap on a 1500 is one of the many things I seen written about but can never remember

IIRC it goes on the (o/s?) front engine mount

so adding a second from the chassis to the gearbox/engine flange close to the stater motor is a reasonable idea, might even be a captive nit on the chassis rail but again I'm not sure about that

I don't know the size of earth straps but I'd have it same size as the leads on the battery
Nigel Atkins

It would appear I still have this problem despite earlier thinking I'd fixed it. I bought and fitted a new earth strap and the car started ok a few times over the course of yesterday evening, and this morning, but after a short drive of a few miles I'm back to square one. Turn the key, starter engages but barely turns over just like a flat battery.

I checked the battery with engine off, engine running and running with electrical load etc and voltage seems ok, so I'm now thinking the next logical step is the starter motor itself? Unlike many of the other components on the car it looks old and possibly original.

When I fitted the earth cables I checked other points such as the solenoid terminals and that all seems clean so I have to suspect the starter.
P Robson 1500

I had a similar issue a few years ago, starter difficult to turn.
On much closer inspection, with me with my head as close to the starter motor as possible while someone else cranked it, i noticed that the connection to the solenoid from the battery glowed red during cranking.

I removed the wire, put a new connector on the end and also some copper washers and new brass nut and gave the connection on the starter motor a sanding down with some smooth wet'n'dry.
After that it worked fine, and the connection cool to touch during cranking.

Andy Phillips (frankenfrog)

Andy...

that sounds very logical, well written.

Prop
Prop and the Blackhole Midget

Could be poor earthing of the body of the starter motor as they rely on earthing through the motors body
mark 1500 nearly on the road

Thanks Andy, I'll enlist a helper and have a close look. It may be that some wires are corroded under the sheathing and aren't as good as they seem.
P Robson 1500

Mark, earlier I ran a separate earth cable from the starter mounting bolt directly to the negative battery strap on the bulkhead. Initially I thought this had helped but apparently not.

Will report back after I've had a further poke around the wiring.
P Robson 1500

poor earthing of the solenoid to the car body because of rust, crud, dirt or fresh paint can hinder starting

poor starting of a hot engine is generally a wide subject matter with many causes and solutions - and many different threads and posts on the matter on these forums

often thoroughly checking the basics is required - such as you've put, electric cables, wires and connections can look OK until you look under the surface

or the running of the car or heat that builds up after an engine is switched off can cause connections to be poor or things to move with the heat or running or possibly overheating

a good and thorough service usually finds many of these problems or prevents them leaving just the more awkward ones to find
Nigel Atkins

Bill is right and so is everyone who agrees with Bill :-)
Nick Nakorn

Spent a bit more time on this. I removed the solenoid, cleaned up all the surfaces and connections and put it all back together, and also removed and checked the condition of all the cables from battery to starter motor.

When I went to start I got the same barely turning over. After a few attempts it didn't even try to turn and I just heard the loud clicking of the solenoid. So I charged the battery overnight and tried again now, still the same, only solenoid clicking.

Just to be clear, despite the thread title this is now happening all the time, not only when the engine is hot which may have just been coincidence initially.

To me, it is all pointing towards the starter motor being burnt out. I am assuming for now that because the solenoid is audibly clicking that is ok, though I will double check with the aid of a helper and volt meter later. There's not much to the starter circuit and it seems I have checked and cleaned up every part of it, leaving only the starter which hasn't ever filled me with confidence since day one.
P Robson 1500

just to rule out it being a battery issue can you attach jump leads from another car to your battery and try it again ?
Andy Phillips (frankenfrog)

I would agree changing the starter motor is the next step.
If it is the original one, it could well be on its last legs anyway.
JB Anderson

Could be battery what voltage have you got fully charged I had one which showed 13v fully charged but would not start car even with jump leads connected turned out to be a faulty battery less than a year old.
mark 1500 Lights on at the end of the tunnel

Battery is showing 13.2V fully charged and it was up to 14.4V when I checked it while running previously. I noticed a date on it too, 06/2013.

I have just hooked the car up to a new spare battery I bought for my 4x4 and I get the same result of a clicking solenoid, so it would appear my starter motor has met its maker.

Can someone suggest the best place to buy one - MGOC? and are there cheap replica parts to avoid out there?
P Robson 1500

given it's a standard Lucas 5 inch starter used on literally millions of cars in the last 40 years, I'd try the local motor factor or accessory shop first.
David Smith

I would agree with David, buy it locally and for possibly less than from a 'specialist.'

The shop would usually take your old unit in for exchange too, which shouild save you paying a premium for the new one.

Whomever you buy from (MGOC, Leacey, Moss or the rest) you will not get a brand new unit from the BMC/Lucas factory.

All such parts now in circulation will be rebuilt and tested reconditioned units.

Even factory parts for your 'daily driver' will be supplied under he same conditions.

So pay the least get the same, ;-) .
Bill1

I would look localy some will refurbish yours are exchange also any problems you can sort quickly. I know from experiance bought a turbo online and had trouble took weeks to sort.
mark 1500 Lights on at the end of the tunnel

Thanks to all again for the advice. I've ordered a starter from a local motor factors who are taking my old one in exchange, only £65 for the new one so can't complain.

Before I ordered it I removed my old one and tested it direct to battery with no sign of life whatsoever. It wasn't a particularly pleasant task removing the lower bolt with the car at axle-stand height, but it's another added to the list of things I can now do.
P Robson 1500

This thread was discussed between 02/03/2014 and 26/04/2014

MG Midget and Sprite Technical index

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