Fuel Delivery Issues

[MikeJohnson]

I have a 94 GMC Seirra, 4.3ltr, 5-speed, 4x4.

 

Ok, so If the truck is cold it will start first crank, but after it has run and you shut it off then try to start it the fuel pump will not run. I traced the problem back to the oil pressure switch. This worked for 2-3 weeks, and now it is back to not starting the second or third time after it has run. Now that i changed the switch it happens less frequently, so it could start 20 times in a row then the 21st the fuel pump won't run .

 

But since the oil pressure switch was replaced, everytime the fuel pump dosen't run, there is a squeal coming from the dash (pcm i belive), the squeal will go on for about10-15 seconds, then quit, with the ignition still on, a few seconds after the squeal stops the fuel pump will start up and the truck will run.

 

The truck has the following new parts-cap and rotor, oil pressure switch, fuel pump, sending unit, relay and fuse, its got spark when the fuel pump won't run and i have traced the wires from front to back and up and down, and they are fine.

 

Thanks In Advance,

Mike

[TexasAl]

Have you checked for power at the fuel pump when it is doing this? That would be an important step. If the fuel pump has power,but it is not sending fuel, then the pump is bad. If it doesn't have power, go up to the fuse box, and see if the fuel pump relay is getting the signal from the PCM. If it isn't then you might have a problem with your PCM/PROM. Good luck.