Justs replaced fuel pump in my '74 2.0 liter, has good pressure(35), until ignition is turned off! Presure then drops to nothing?? Ideas???

1.) Check valve in pump is gummed open or not functional .... pressure leaking past to return line.

2.) Injector (engine or cold start) stuck open, leaking fuel into cylinder or plenum.

3.) Fuel line leaking

or

You have a fuel puddle under your car

Also, if you are set at 35 psig, you are 6 lbs higher than spec .... injectors are being held open by fuel pressure alone.

Funny, mine does the same thing. When you turn the engine off the pump stops running. Actually, fuel pressure is not important when the engine is not running. When it is running, pressure should be around 29 lbs.

With pump off ... approximatley 20 lbs pressure is held in the system for a few minutes (like 10??) for starting purposes. Don't suppose it makes much difference as in the "on " position, pump will run for a few seconds to build pressure. When going to "start" pump is running again until engine starts and brain "proofs" circuit which makes the pump run continuously.

There is no possible way that 35psi can hold an injector OPEN. If anything higher F.P. will keep it CLOSED, but that would take over 70p.s.i.

the common misconseption about the inj's. in our cars are, they cannot operate or operation is affected at anything over 29psi. They will function just fine at higher pressures.

The reason the FP on the inj. system is set to 29psi is to get the correct fuel flow out of the inj. for the PW which is determined by the ECU.

The inj's. for these motors are huge compared to the engines fuel req..

What do you do if you want LESS flow from an inj. ? LOWER the press. MORE flow, raise it!

Modern fuel systems run at 43 to 50 psi. , inj's operate just fine.


Now, you may have inj's that are shicking and staying open or worn and leaking past the pintle. The check valve on the pump may be bad also.

To check the inj's., remove one inj. at a time and put it over a container, fire up the car for a sec. and shut it down and see if the inj. is leaking at the tip after the motor is off. Reinstall the inj. and do the same to the next inj.

Do each inj. ONE AT A TIME

Keith