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Non Return Valve in Flapper Type EFI


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hello people,

I am running twin external pumps on my Flapper type 3.5 EFI Traka, can anyone tell me if there should be any type of non return valve in the fuel feed/return lines as the fuel pressure disappears within a couple of seconds of turning the engine off?

Roger <_<

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Hi Roger, the pumps should have non-return valves in them. Try re-plumbing to just one of the pumps at a time and see if either holds the pressure. Also look at the fuel pressure regulator, it could be leaky. Beyond those possiblilities is a dribbling injector, but that would probably show up on a plug check as one very rich cylinder.

johnw

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Hi Roger, the pumps should have non-return valves in them. Try re-plumbing to just one of the pumps at a time and see if either holds the pressure. Also look at the fuel pressure regulator, it could be leaky. Beyond those possiblilities is a dribbling injector, but that would probably show up on a plug check as one very rich cylinder.

johnw

Hi JW

Good to hear from you how is the leg? are you running around yet?

The pumps are two old BMW 735 pumps (specs as per the FSE site) picking up from each end of the tank joining at a 'Y' piece just before the filter, one is noisier than the other so will check running just one at a time.

It idles perfectly at 800rpm and picks up well from there but i cant give it a blast as the bodywork isnt fitted and its not road legal yet.

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Are they designed to run as lift pumps? A lot of pressure pumps don't like having to suck - I know several people who have cooked a number of fuel pumps finding this one out. Running noisily is a clue that the pump's not happy, the one on the 109 used to do that before I fitted a swirl pot and it would pump vapour not petrol.

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Are they designed to run as lift pumps? A lot of pressure pumps don't like having to suck - I know several people who have cooked a number of fuel pumps finding this one out. Running noisily is a clue that the pump's not happy, the one on the 109 used to do that before I fitted a swirl pot and it would pump vapour not petrol.

Hi FF,

Both pumps are located on the insides of the chassis under the floor below the tank, and are effectively gravity fed. So they are definitely acting as pressure pumps. Both are original Bosch manufacture 058464070 (FP603 type) from mid 80's BMW 735's, maybe they are just old and knackered like me. :unsure:

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