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MG MGB Technical - Break-down after 15 minutes!

My 1966 MGB starts and runs perfectly for the first 15 minutes and then splutters to a stop. After a further 30 minutes unable to re-start the engine then decides to fire-up and the car will drive again. I have recently replaced the coil and condenser which I thought had cured the problem - but sadly not! Any ideas please? Many thanks.
Jonathan Willoughby

Too much fuel pressure is one possibility ... sounds like it may be flooding. When it restarts, does it kind of cough to life, perhaps with a puff of smoke? Might wanna get a cheapo fp reg & see if that licks the problem.
Bill Withum

Does it cut again when you eventually restart?
If so, check the fuel tank. has this been replaced at all? If not, rust particles may be blocking up the small filter on the pick-up pipe, and after 30 minutes dropping off allowing fuel to flow. One way to check is to blow down the fuel line towards the tank and if the car starts straight away, then you need to check the tank out.

Coils are also known to gie problems despite being new, and check to see if you need a ballast or have one?

HTH
Martin

Or have you fitted a non vented filler cap?

Try releasing the cap when the engine stalls - if there is an inrush of air then you need a new cap.
Chris Betson

Try disconecting the carb vent line at the carbs. Turn ingnition on but do not start the engine.(to operate the fuel pump) Watch for fuel leaks. There should be no leaks unless a needle valve is not working properly. If there is no fuel leaks start engine and check again. My 1971 MGB ran for 15 minutes and stopped. It was the float bowl vent line being pinched when the bonnet was closed. The engine ran fine with the bonnet open. good luck with it..
Jim

Is the coil hot to touch?

I had a very similar problem and it turned out to be excessive impedence in one of the HT leads causing the field in the coil to fail to fully collapse. This in turn lead to the coil overheating to the extent that it couldn't sustain a field properly at all, so the sparks were to weak to ignite the mixture.

In my case replacing the leads wasn't enough to fix the problem on its own because the overheating had distroyed the coil too.
Carl Kambites

This thread was discussed on 10/06/2003

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