Scootertrash

97 Chev K1500 4X4 5.7
Can a fuel pump allow the gas to drain back into the tank? If I turn the key on, but not start the engine, fuel pressure goes to 60 PSI, but pressure drops immediately after the pump shuts off when it reaches pressure. I pulled the upper intake and no fuel is coming out of the regulator, none comes out of the poppet nozzles and none comes out of the return line hole. All I can think of is the pump is dying and the fuel is draining back into the tank. I've never heard of this before. Have you guys?
Thanks!
Scooter

x1cn18

it is very possible

in2pro

nothing should come from the poppets unless the injectors are told to fire, 60 psi is pretty healthy, the return line is just that, but with the engine off for some time disconnecting the fuel line should yield some fuel leakage, if its not them its probably leaking back down...
What brings you to ask the question?
are you having starting problems?

Scootertrash

Problem originally started as lack of power under hard throttle, but drives fine "normal". Truck seems to struggle when I try to go to "passing mode". Truck downshifts but seems starved for fuel. Fuel pump also seems abnormally loud at times, but not consistantly. I hooked up the fuel pressure gauge and pressure shoots up to 60 but as soon as the pump cycles off, pressure drops to 10PSI or less in a matter of 15 to 30 seconds. My wifes 99 Tahoe holds pressure fine, and I seem to remember this truck doing that too.

I suspected the fuel pressure regulator, which is why I went into the upper intake. There was no evidence of fuel leakage at the Fuel Pressure Regulator, so I placed a paper towel under it and had the wife cycle the pump (truck not running). No leakage. I had also cycled the pump(truck not running) before I removed the plugs to check them. I wanted to see if there was an indication of excess fuel in any of the cylinders, all cylinders had nicely colored plugs and none were wet from the pre-removal cycling of the pump. I figured if I had an injector that was stuck open it would have leaked thru the poppet nozzle into the cylinder.
After checking the Fuel Pressure Regulator, I removed the poppets from the intake to see if indeed I had any leakage there, possibly due to a stuck injector. No leakage at the poppets. I then removed the return line from the injector housing to see if fuel was leaking back thru the FPR into the return line. No fuel leakage at the return line either.

So, to summarize:
No fuel leakage from the FPR into the intake
No fuel leakage from the poppets
No fuel leakage from the FPR into return line
I can see no puddling under the truck where fuel could be leaking

The only place it seems the pressure could be going is back thru the pump. I opted to check the easier stuff rather than to tear into the pump right away, since we all know what a PIA it is to do. The only way I've had pumps fail before is it just fails and stops running. I've never had pressure leak back thru one, although I'm sure it's possible. I'm up for any other suggestions tho.
Thanks!
Scooter