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MG MGB Technical - Difficult to start when hot

ok first of all I went to achive and read some of the threads about this starting problem that we all have to face to.

I try to find the point concerning my MGB GT 72.
When cold she has sometimes difficulties to start at first and second try but at the third one usually she fires. I never used a choke to start her in cold or hot weather. Sometimes she does this thing which is: I turn the key, I 've got the klick of the fuel pump and the engine is starting but not firing and she shakes from everwhere, it is obviously a fuel starving problem, so when she does that I just knock a bit some points and then she starts.
But I noticed as I now run a bit more for longer ride that if I stop the engine when hot and try to start it directly she won't fire and she shakes again.

So conclusion as the MGB Workshop manual say could be: fuel pump misfonction, valve dirty, choke maladjusted or diaphgram or filter blocked! ok so yesterday after a ride, she stops for the first time and I couldn't restart her ... so I just let her cooling gently and went on the beach, after few hours I started first try perfectly!

SO I am keen to conclude that it could be a maladjusted choke, am I right do you think ? and the workshop manual gives the cause of the problem but not the cure ... what is the cure for a maladjusted choke if it is the case?

thanks a lot

Once in a concen, a friend of mine with a Mga, also had a problem starting is car and i heard some saying to change the Ht coil, and apparently it worked...not sure if anything else.

It's a diificult one to start on as it most likely comes under the "a bit out of tune" category. How do the spark plugs look? Black and sooty or clean and grey (you won't see brown now thanks to modern fuel). Sounds like you could do with a full tune up starting with the points, timing, plugs and valve clearances before tackling the carbs. As a possible quick fix, is your carb heat shield in good shape? If it's missing or broken the heat of the manifold causes a vapour lock in the fuel line.
Steve Postins

Steve's right that your car needs a full tune up by someone knowledgable on these engines and in SU carbs in particular. My feeling is that the engine is running very rich and this could be due to the choke not being set up correctly and or the mixture setting of the jets being well out. The clue to this is that you say the car will start without the choke on a cold engine. How long is it since the air filter elements were changed ??
Iain MacKintosh

thanks for your advice I think I really have to let the specialists now have a look under the bonnet of my GT... I have new air cleaners with new air filters but haven't tried already to change them (maybe not by myself, is it difficult to do it?) and I have no ideas if they have been changed but I would guess that they haven't been changed since ages ....

That was only me clutching at straws and didn't think you would be so lucky as to solve the whole problem by changing the elements. They are easy to change but setting up the carbs from scratch if they are badly out of tune requires fairly in depth knowledge and I would advise you to seek specialist help. Perhaps however there is a club in your area, why not check this out and maybe go along as I'm sure they will be willing to assist.
Iain MacKintosh

This thread was discussed between 21/03/2005 and 23/03/2005

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