94 Jimmy, fuel pump or regulator or ???

[GT55]

First off, after the vehicle runs for a while, turn it off it won't start back up. So here is what I did. Hooked up a fuel pressure gauge at the back of the plenum. Turn the key on and listen to the fuel pump whine for 2-3 seconds. As fuel pump is whining the gauge goes to about 55-60 psi. When the fuel pump rely clicks and the fuel pump stops whining, the pressure gauge falls to about 20 psi and stays there. I split the plenum and did this test again. The pressure gauge gave the same readings and there were no leaks anywhere in the plenum.
If this is a fuel regulator problem, how can I check it? If it is a fuel pump problem, how can I check it? If it's something else please advise...

Thanks All...

GT

[Airjer_]

Under the vehicle you will see two rubber lines near the fuel pump. One is the pressure line and one is the return line. Pinch off the return line (only if it is rubber!) and key it up. If the pressure holds its the regulator (unlikely). If the pressure still drops its probably the pump. Have somebody key up the vehicle. as soon as you hear the pump stop running pinch off the pressure line. If it is the pump (likely) pressure will remain steady until you unpinch the pressure line.

[MT-2500]

Originally Posted by GT55

First off, after the vehicle runs for a while, turn it off it won't start back up. So here is what I did. Hooked up a fuel pressure gauge at the back of the plenum. Turn the key on and listen to the fuel pump whine for 2-3 seconds. As fuel pump is whining the gauge goes to about 55-60 psi. When the fuel pump rely clicks and the fuel pump stops whining, the pressure gauge falls to about 20 psi and stays there. I split the plenum and did this test again. The pressure gauge gave the same readings and there were no leaks anywhere in the plenum.
If this is a fuel regulator problem, how can I check it? If it is a fuel pump problem, how can I check it? If it's something else please advise...

Thanks All...

GT

\

Is the leak down the only problem it has?

As said pinch off return line and recheck.

But also a fuel pum can leak pressure back threw the pump when off.

What engine and code?
First thing.
You should run a full fuel pump pressure test on it.


If Specs on it is 55/62 lbs of pressure
Here is some guide lines of fuel pressure checking.

Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines should have 55-66 fuel pressure.
Cold start should be 55/62 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 55/62 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
If pressure does not come up with return line pinched or blocked off.
Go to fuel filter and hook a gauge direct to a line at fuel filter.
Pressure should come up to 75 or more and will hold after fuel pump is turned off.
If it leaks down there after fuel pump is turned off it is LEAKING BACK THREW PUMP CHECK VALVE OR PUMP MODULE LINES.
Post back your fuel pressure readings.
MT

[Airjer_]

Go to fuel filter and hook a gauge direct to a line at fuel filter.
Pressure should come up to 75 or more and will hold after fuel pump is turned off.
If it leaks down there after fuel pump is turned off it is LEAKING BACK THREW PUMP CHECK VALVE OR PUMP MODULE LINES.

Or pinch of the pressure line after the pump has shut off. If you don't have the adapters to hook up inline at the filter than pinching the pressure line after the pump stops running does the same thing.