Fuel Pressure Loss

[Ricker]

The long my car sits without running, the more time I have to keep turning the key to get the fuel pump to get fuel to the engine and build up the pressure (the fuel pump only runs for a second or two before it stops). Once the fuel is there and pressure is up the car starts perfectly hot or cold. Question number 1 - I had the fuel injectors checked and cleaned, the fuel is not leaking there. Where else should I look? (I do have the new modern fuel pump installed for some time) Question number 2 - Is there a way the jumper something out so when the key is turned on the fuel pump runs continuously? Question number 3 - Is this bad for the fuel pump then?

[Bitsyncmaster]

I ran a test to when control pressure would reach 40 PSI (warmed up engine) and it was less than one second running the OEM pump and OEM (large) accumulator. If you find yours takes longer to reach that pressure first thing I would check if the accumulator is leaking. Also check the voltage at the fuel pump (jumper the RPM relay).

[Ricker]

I ran a test to when control pressure would reach 40 PSI (warmed up engine) and it was less than one second running the OEM pump and OEM (large) accumulator. If you find yours takes longer to reach that pressure first thing I would check if the accumulator is leaking. Also check the voltage at the fuel pump (jumper the RPM relay).

When you say the fuel accumulator is leaking do you mean externally?

[Bitsyncmaster]

When you say the fuel accumulator is leaking do you mean externally?

It would leak into the return line to the tank if the bellows inside were leaking.

You can pull that return hose off and run the pump to see if fuel is flowing from the return.

[Rich]

It would leak into the return line to the tank if the bellows inside were leaking.

You can pull that return hose off and run the pump to see if fuel is flowing from the return.

Note to those wondering which of the 3 accumulator connections is the "safety fuel return line", the one that should be pulled to check for a busted accumulator diaphragm, it's the single hose on the end of the accumulator closest to the engine.

That hose is normally dry. Its only function is to direct any fuel that leaks past the internal diaphragm safely forward into the fuel tank. Until the accumulator is replaced.

[Ricker]

It would leak into the return line to the tank if the bellows inside were leaking.

You can pull that return hose off and run the pump to see if fuel is flowing from the return.

Understand. Will do so when I can get under there. Kinda tough place to get to.

[82DMC12]

Understand. Will do so when I can get under there. Kinda tough place to get to.

This problem could also be caused by a failed check valve at the fuel pump. There's supposed to be a check valve either integrated in the neck of the pump (long neck style) or it screws into the neck (short style).

[Jonathan]

Try this instead: confirm the adjustment of your idle speed motor microswitch. This is the one that gets actuated when the throttle spool and arm are at rest. There are two adjustment pegs on the lever arm. Lower one corresponds to the rest position of the butterfly valves inside the manifold (you can't see them when everything is assembled). The upper adjustment peg engages the idle speed motor microswitch. You want that microswitch to click just prior to the arm and throttle spool coming to rest. You can listen while the engine is off and you are moving the throttle spool with your hand. Get it so the microswitch clicks at the exact moment the arm stops at rest, then turn it in a half turn more (so it's engaged at rest versus not engaged). Your lack of apparent fuel pressure (while not actually measuring the fuel pressure) might be a lack of air and not fuel. Give it a try and report back. It's easy to put it back the way it was if you're in doubt. Just make note of where it was when you started.

[David T]

When you are checking the accumulator you must remove the hose from it and block it off. Otherwise fuel returning to the tank from the PPR will come out. If fuel comes out of the accumulator with the "safety" hose removed it means the diaphragm inside is bad and the accumulator should be replaced otherwise you will have problems restarting the car when it is hot. The temporary "fix" is to do the "plug swap" to get the motor started till you can replace the accumulator.

[Helirich]

The long my car sits without running, the more time I have to keep turning the key to get the fuel pump to get fuel to the engine and build up the pressure (the fuel pump only runs for a second or two before it stops). Once the fuel is there and pressure is up the car starts perfectly hot or cold. Question number 1 - I had the fuel injectors checked and cleaned, the fuel is not leaking there. Where else should I look? (I do have the new modern fuel pump installed for some time) Question number 2 - Is there a way the jumper something out so when the key is turned on the fuel pump runs continuously? Question number 3 - Is this bad for the fuel pump then?

When you say “the longer it sits” , how long are we talking? If you are talking hours, look at the accumulator, but if you are talking weeks, I don’t think that’s your problem. It may be a weak pump or somewhat clogged fuel filter.

When you say “I have to keep turning the key”, do you mean cranking the engine? If so, try just turning the key on and off (without cranking). Every time you turn it on, it should run the pump for a few seconds. That way the pressure comes up without heating up your starter and straining your battery.

There is a way to jumper the rpm relay and turn the pump on, but you shouldn’t have to resort to that. (It’s mainly used for trouble shooting)