I just bought a 1993 Chevy Silverado 2500 and have run into some snags. First I want to say that I know nothing about diesels so my problems maybe simple. It wouldn't start the day after I bought it so I thought the batteries were bad so I put two new batteries on it. Still wouldn't start so I thought the fuel filter might need replacing so changed it. I didn't know that you had to refill it with diesel so that was an issue. I spoke with a family member and they said I had to get the air out so we did that and still not starting. We opened each injector and it seemed like we were not getting much fuel so I thought the fuel pump might have been bad so I replaced it and still nothing. My question is does the fuel pump make any kind of noise when it comes on or is there a way to tell if it is working correctly? Is there a relay that I should check. Any help would be appreciated!

 

you should hear the lift pump turn on when you put the key in run. there is a bleeder screw on top of the fuel filter housing to bleed the air out while your running the lift pump

 

It will only run in crank or engine run mode on OBD-Is (pre-96) oil pressure switch (OPS) is dual function powers the lift, and gives dash pressure display. In engine crank you bypass the >4 psi oil requirement to power the lift pump.

To test lift pump, put +12v to PIN G of the ALDL port under the dash, and if it's functional it will move fuel, that said you can have a purring lift that doesn't move fuel, with 12v applied to pin G and filter mgr vent cap open you will purge air. If system is airbound it will take extended cranking to purge the air from IP & injectors, but if glow system is healthy (another diagnostic routine) then it should start.

Once started there is a brass valve with T handle front center of engine, this is the mgr water drain, also handy place to check health of the lift, apply test gage there and you should have 4-5 psi with healthy lift pump, if 2 then lift is weak, if 0 then OPS is not providing power to the lift and you need new OPS.

Once that is proven, go for test drive with that gage still hooked up on long rubber hose into the cab (don't pinch the tube or you'll deadhead the reading) should be 3-4 min while at highway speed, and not drop below 1 psi on hard accel