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MG MGB Technical - electric fuel pump

I have been having problems with the engine flooding and the car not running. Question: Is it possible for the electric fuel pump (77 MGB) to push more fuel to the carb then it can handle thus causing the engine to flood out? I have had two carbs on the car with the same result. I am getting full spark and the engine turns over, runs for a minute or two then floods. Pull the plugs and they are soaked.
Any suggestions will be welcome.
Jim McDowell

I am a bit vague on your situation, but my gut level guess is that the pump is possibly providing way too much pressure for your carb. Generally speaking, SU and Zenith Stromberg Carbs are only designed to handle a very low fuel pressure - somewhere in the neighborhood of 1 - 2.5 psi. Many aftermarket electric fuel pumps provide much higher pressures than this, with the result that they blow the float valves off of their seats, and allow a flooding condition as you describe.

To correct your problem, I would first figure out if your fuel pressure is too great. Buy or borrow one of the inexpensive Vacuum/Fuel pressure guages from Sears or Harbor Freight and place it in the fuel line securely and then simply turn on the ignition. You should get a reading on the guage and that will tell you how far off your pressure might be. If, however, it is correct (as per above), then you probably need a new float valve or you have some crud holding it open. If the pressure is way high, then you should then crawl under the car and find out what sort of pump your car has now, as any pressure higher than that specified will likely mean a non original, aftermarket pump.

If you find you have an aftermarket unit, and your pressure is way high (above 5-6 psi), I would strongly suggest you get another of lower output pressure. If it is nominally higher, say 5-6 psi, you can rather easily continue to use it with the addition of a fuel pressure regulator between the pump and carb. These come in different forms, but none are very expensive and you can dial in the correct pressure you want using the pressure gauge. In fact, I would recommend using a fuel pressure regulator with any pump used other than the OE SU pump. Good luck.

Bob Muenchausen

Unless fuel is pumping into the emissions plumbing then I doubt the pump is the problem, and even if it is it could just as well be the float valves. Maybe it is just running very rich through poor adjustment. What carb is it? If Zenith maybe the auto choke is stuck on.
Paul Hunt

This thread was discussed between 08/04/2002 and 09/04/2002

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