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MG MGB Technical - Still not starting

Hi,
I seemed to have changed a lot of things but still cannot get my MGB (1980 version) to run (I bought it recently - it has stood for ten years!). The latest action I have performed is to strip down and clean both carbs. I have fuel getting to the float chambers but when I turn the engine over I would expect a little fuel on the plugs, but there isn't any. Is there something fundamental I am missing to how the fuel gets to the plugs.
Help......

Thanks,

Andrew
Andrew

Blocked jets? Choke working properly? With the choke out and much cranking you should eventually soak the plugs i.e. flood the engine and get a strong petrol smell. Before it floods the plugs should have a petrol smell but not be wet. If there is no petrol smell no fuel is reaching them.

Paul Hunt

All the jets are/were clear as I stripped the carbs down and cleaned all the muck off. I am not sure about the choke working correctly, I have a feeling it is. I haven't been able to soak the plugs but I believe there may be a very, very faint smell of petrol on the plugs (difficult to tell after you have been handling petrol...). Maybe it isn't a fuel problem after all??

Andrew
Andrew

Andrew, have you checked that your fuel pump is working? It should click a few times and turn off once it has reached pressurization. You can check by undoing the fuel line, sticking the end in a jar and have someone turn the key on (don't start the car).

Occasionally after the pump is left standing for a long period the points tend to stick. If this is the case strike the pump a few blows to get it going. You may need to take the pump out and clean/replace the points or diaphram. Or do as I did and just get a new pump.

Good Luck
Luis

Have you done a compression check? If it has stood for ten years the piston rings may be stuck. When you cleaned out the float bowls did you use tissue/ kitchen roll, it's easy to get a small amount of tissue in the very bottom of the float chambe and block the fuel outlet to the tube below the carb. Timing, is it set correctly, be sure it's not 180 degrees out. Fuel, put a clean rag over the carb openings, have someone crank it over a few times, take away the rag and see if the carb is wet inside or smells of fuel, careful though as it might start doing this.
robert bryan

I have replaced the fuel pump with a brand new one and tested that it works ok by switching on and it running the fuel line into a jar. The float chambers are actually full of fuel ok. Incidently I did clean the carbs with lint free cloth and wynns carb cleaner (very impressive stuff!). When I am cranking the engine the oil pressure does rise to around 120/130, Could it be the timing? or coil?
Andrew

Andrew

If fuel's there the next thing I would check is for a nice fat spark. Take out a plug and wedge it against the engine block, so it's held firmly in position and has good earth contact with the engine.

Then turn the engine over or get someone to do it for you. Observe if there is a spark between the electrodes of the plug.

If you have a colour tune, fit this to one of the cylinders and watch for the spark (this is probably safest method).

If no spark check your rotor arm and Ist. Cap.
Check Voltage on LT side of coil

Remove HT lead from centre of Dist. position this next to the engine block (other end of lead still connected to Coil). Turn over the engine, end of lead needs to be about 3mm from engine block, and look for spark.

Better to tape the lead to the block and keep your hands away for safety just incase there are any stray Volts flying around.

Steve
Steven Williams

I am getting sparks in all the right places, they are good sparks as well. I have changed the battery, plugs, plug leads, dizzy cap, points, condensor, coil and fuel pump. But I still not convinced the fuel is getting to the plugs as they are not even damp after cranking for 3 x 20 secs, but I do have fuel in the float chambers. I will check the timing this weekend, but it is all getting rather boring now...I just want it to start!...smile
Andrew

Still sounds lack of fuel to me, plugs should be wet after 60 secs of cranking with the choke out, smelling strongly of fuel as a minimum. Have you checked the choke yet? Jets? But are you sure you have got the firing order correct - 1342 anti-clockwise? Sure each plug is getting its spark at the correct time i.e. TDC on the compression stroke and not the exhaust? You need to think it through from first principles - an engine needs air, fuel, compression and spark at the right time and in relatively correct quantities to fire.
Paul Hunt

Pull the plugs, shoot a bit of WD-40 in each hole, then quickly replace the plugs and try to start it. If it runs for a second or two, you'll know for sure that your spark is getting to the cylinders at the right time, and that it's a fuel delivery problem. If it won't fire at all or fires very erratically it's most likely a timing problem.
Ken Lessig

Andrew, did you try the rag over the air intakes? If fuel is getting through the carbs will be wet as well as the plugs. Where are you in London, how far fom Basingstoke are you?
Rob.
robert bryan

Andrew: I agree with Paul. I would do a static timing check as per the Haynes manual. If the engine fires with starting fluid (aka ether) than the timing is probably close enough. Even if the plug wires are mixed it will start and run, albeit poorly. SU carbs are fairly simple devices. Unless the jets (and their lines from the float bowls) are totally clogged it should at least start with full choke.
Andrew Blackley

Firstly thanks for all the replies,

I tried the rags but did not get much fuel on them - but there was a faint smell of petrol.
I have also tried easystart down the plug holes without any success.
I am beginning to think that it is a timing problem (possibly coupled with a fuel delivery problem!).
The plug leads are on correctly 1342 (1 being near the rad..)
The choke is operating fine as well.
I will attempt the timing on Sunday (as I am working Sat..groan) - I now have to work out the degrees BDC...

thanks again all...

Rob - I live near Epping about 80 miles distance.
Andrew

Hmmm, a bit far really. I hoped you were nearer like Sunbury or something.
Anyway, If the fuel is getting through and you have a spark, then the engine will fire, even if 180 degrees out, it will just back fire as it burns off the excess fuel. I think it's fuel related, sorry chaps. Stick with one thing at a time. Make sure the fuel is getting through, take off the fuel pipe to the bottom off the float chamber and use a foot pump to be sure it's clear. Check you have pressure from the pump. I had a problem with one of my carbs bogging down and it turned out to be a blocked pipe from the fuel chamber.
If you have a footpump with the adaptor, the pointy one, to inflate a football, use this from inside the carb once you've removed the needle. you should see lots of air bubbles in the float chamber. If all is well then turn to the ignition, first remove the rocker cover and put the car in gear, push it forward to turn over the engine, unless you can get a spanner on the nut that holds the pulley on.Turn over the engine to line up the marks on the pulley, I think it may be 10 dgrees BTDC, look at the valves on No 1 piston and see that they're are closed, i.e. you can wiggle the rockers and that the valves on No 4 are open. get a small bulb that is wired and put one wire on the feed to the dizzy and the other to earth,the rotor arm should be pointing to No 1 electrode, turn the distributor anti clockwise until the light goes off, then clock wise until it just comes on. This will set your timing accurate enough for the engine to start.if you are still stuck then e-mail me and I'll give you my phone number, or go to www.robsfrogs.org.uk and get it fronm there.
Rob.
robert bryan

If the float chambers are full and you blow in the overflow pipes (one at a time) I would expect fuel to come up through the jets - lift the piston by hand for a clearer view.
Paul Hunt

Andrew

If the carbs have been overhauled they will need resetting, have you done this?

Have you made the initial settings of the needles as per the manual.

ie- Set each jet level with the shoulder at the base of carb. and then wind back (I think it's about two turns but I'm not sure).

Steve
Steven Williams

I have blown through the overflow pipes and fuel comes up through the jets fine.
I reset all the screw settings back to what they were in the beginning.
I rechecked the timing on Sunday and it was spot on.
I have had someone suggest that maybe all the rings are stuck, so there is no suction from the pistons to pull in the fuel/air mix...could it be that?
Andrew

How open are your butterfly valves in the carbs?


Tatty

Trust you are aware that the distributor rotor goes anti-clockwise - essential info in checking 1-3-4-2 firing sequence. I had assumed clockwise, like the pulley and wondered why the new engine ran rough.
B.J. Quartermaine

The butterfly valves are open when they should be..and I have watched the rotor arm go round anti clockwise ok..
I have been told it is worth checking the valve timing as the woodruff keys sometimes come out but due to the design of the engine the valves wont bend etc but the engine will never start....

I will get this thing going!!!!...smile
Andrew

Andrew, is the valve timing correct, have you checked this. To check if the rings have stuck, you best use a compression tester. These can be bought from most auto stores, they're not expensive although borrow one if you can because they aren't an every day item you'd use. Out of curiosity does your battery go flat after constant cranking of the engine?
Rob.
robert bryan

I too had an MGB that had stood (never touched) 7 years. I knew it had run before so it was just a case of unsticking things. I had to strip and rebuild both the SU pump (diaphram had split) and the carbs. Float had stuck to bottom of bowls. (Nice flood of petrol in garage). Took about 2 weeks to get started. Compression was a bit weak so added WD 40 to spark plug holes and turned over by hand backwards and forwards. Then ran on starter motor for a few seconds at a time. Compression was a bit better.

Still couldn't get it to run even with good spark. Eventually (Don't really recommend this but it worked for me) I used my old camping gas stove. Pointed the gas outlet down the carb choke and tried to start it. Ran first time. Let it run on gas a few seconds, pulled the gas away and it died. Repeated the exercise a few times and it has ran perfectly since. Done another 24Kmiles with no side effects. Compression is very good now. Could only put the non starting down to low compression. Gas obviously didn't need much to start and running with good oil pressure seemed to restore compression.
Stuart Robson

Andrew,
Robert and Stuart are likely to be on to something with the compression. On my first MG I once destroyed a valve and knocked a hole right through the piston. As a result had no inlet manifold vacuum, therefore the SU carbie pistons wouldn't lift therefore not enough petrol.
I have not tried the following so I advance the idea cautiously,(ie. if anyone thinks it's a dumb idea, speak up) but I was told by a mechanic that with poor compression motors not a bad trick is to remove the sparkplugs (again, sorry) and pour a little oil in, on top of the piston. The theory is that the oil will settle on top of and around the piston rings and give a temperary seal. You won't need much oil, use way too much and I think you're likely to do damage, obviously there must be room for the piston to complete a compression stroke. Use a piston at TDC as a guide perhaps. Replace the plugs (before the oil drains) and start her up.
You're going to love driving an MG, the definitive sports car, everything else are just copies.
Peter

Andrew: Do you have access to a set of carbs from a working car that you can swap onto this one temporarily? Carbs can be a real pain. My Bro in law couldnt get his 71 roadster to start after sitting only a few months, no fuel getting to cylinders. The jets had gotten clogged up somehow.Then again I swapped a set of carbs fom a car that I know sat unused for several years onto another car and it fired right up!
william fox

I will be getting a compression tester this evening, to check once and for all. I have been told that if the compression is low (maybe because petrol has washed the bores clean..), pour some oil down the plug holes if the compression rises it is a problem with the rings, if it does not then it could be the valve timing (I have never done valve timing so I hope it is just the rings!!).
Robert - The battery is new and yes it does go flattish after days of cranking...
William - No I haven't got access to a good set but I believe the jets are now clear..
Andrew

Get someone to help when you do compression test. They can hold down the accelerator (Opens the butterflies). It's probably worth pulling all the plugs before you start just to take a little load off the engine.

If your rings are well and truly gone you'd wish it was just valve timing although I can't see why that would change unless someone has stripped the engine right down.


Good luck!
Stood for 10 years - What's the body like?????
Stuart Robson

This thread was discussed between 21/05/2002 and 31/05/2002

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