LOSS OF FUEL PRESSURE?

[captainshane]

I have 2001 Tahoe with a 5.3 liter. 2 1/2 years ago I had the fuel pressure checked. As soon as you turn the vehicle off the pressure would dropped to zero. I was told that it was more in likely the valve in the fuel pump was faulty. Well I change the fuel pump tonight because it has been making funky noises lately. Fuel pressure still drops. 3 1/2 years ago I changed the fuel pressure regulator, could it be that again or something else?

Thanks,

Shane

[Scott K]

I would pull the vacuum hose off of the regulator and see if gas comes out of it while it is running, and then shut it off.

[captainshane]

Ya we did that and she was dry. It has us stumped. If a injector was leaking into the cylinder I would see that when I change oil, but the oil is normal looking.

[Scott K]

You wouldnt necessarily have gas in your oil if an injector was leaking.

[captainshane]

Ok.

Thanks wanderingeyes.

[Jeremy airjer W]

Interesting!

[Big Buck Buster]

Disconnect the return line from the injector rail(small line), and cycle the key on then off to see if the fuel is leaking back through the fuel pressure regulator. You may have a regulator that is stuck and letting all the fuel back to the tank even though it is not leaking out the vacuum port.

BBB

[captainshane]

I will try that BBB>

Thanks.

[Jeremy airjer W]

Fuel is going to come out of the return line if you disconnect it whether or not the regulator is leaking. Make sure you carefully do this. If you have your gauge hooked up. Return line disconnected. and key it up you will see fuel coming out until the pump stops running. At that point you shouldn't see any fuel coming out.

What brand of pump did you install?

[Big Buck Buster]

Fuel should not come out of the return till it hits max pressure of the regulator. That is why I suggested this for diagnoses. I have had some bad regs do this before. Just don't keep cycling the key on off, on off, or you will have a lot of fuel coming out of the return. Place some towels under the return to catch the fuel that does come out. While watching the pressure gauge, watch how much and how fast the fuel comes out the return, You should see about 50 psi before any large amount of fuel comes out the return. If you don't have much fuel coming out the return, and the fuel pressure is dropping right off, you may have a bad pump, or more than one injector leaking down. You should notice a rough idle right off the bat if you had a leaky injector(s).

[captainshane]

I don't think it would be an injector (s) because the pressure drops from 50 down to zero in about 3 seconds after turning the engine off. I will try a new reg and go from there. The fuel pump was replaced last night.