ok i'm about ready to pull whats left of my hair out. all year i have been having a major problem with my car, basically what is happening is that i'll be out driving, and sometimes it will die on me as if it ran out of fuel. Now all the parts that have been replaced this year were, spark plugs, plug wires, distributor cap and rotor, ignition module, ignition coil, new venom 21lb injectors, rebuilt fuel rail, new FPR, Fuel pump is a new AC delco, fuel pump strainer, fuel pulsator, fuel filter. The fuel pump relay was replaced last year, and the fuse for the fuel pump is also new.

Last week i went out for a cruise/coffee and the car got to the place i was going no problems, but when i tried to start it up the fuel pump wasn't priming, so of course i had to get towed home, and naturally when i got home the fuel pump started to prime again. I have looked at all the wires coming off the battery, through the relay, under the door sill, and behind the seats and it all looks decent, and power is getting to the relay without resistance going to the pump. When i changed the pump out, i did it the "fun" way and all the wiring continuity checked out on the sending unit, the one thing i still have to check is the ground for the fuel pump under the carpet under the drivers seat.

So my mechanically inclined 3rd gen brothers, what do you think the problem might be, i know that for some reason while the car is driving the pump cuts out and the car dies as a result of not getting any fuel. PLEASE PLEASE help i'm about ready to take it country side and light the #&$^%#@ on fire

 

Well, even though the relay was replaced, it could still be the relay...bring a jumper wire with you for a bit and if it happens again, try jumpering the orange and tan/white wires on the relay harness and see if she fires/runs then. You will at least be able to get home or drive it some from there if you make a good jumper. There is a signal that the ECM sends as well for the pump to work. If the relay doesn't prime the pump, I believe that once it builds oil pressure from cranking it should fire and run as well. I had this issue and i had to crank it for a bit before it would fire until I replaced my relay. Like I said, it could just be a bad relay from the parts store. Either that or the ECM is not sending signal to the pump for whatever reason...bad ground, oil pressure sensor issue, etc. I am pretty sure if it doesn't get an oil pressure reading it will shut off the pumps as a safety precaution to avoid engine damage.

 

thanks dude now another question for ya, i did test the oil pressure sending unit for taking over for the pump and it did work, but could it be that the oil pressure sending unit is on its last legs? i'm not sure when it was last replaced but seems to work ok for both jobs., like i said before i'm gonna double check the ground when its not rainy out(no garage) but it that checks out i might try the relay again. And on top of all the other crap i've dealt with the battery died on my last night :P i think i left the hatch open just enough for the light back there to stay on :P oh well got it boosted today

 

Sounds like relay based on what is working to get her started so far. I would just replace the relay again. Probably just got a bad one...it happens from time to time.

 

done and done will let ya know when the weather clears up round here

 

The OP switch is in parallel with the relay. If the switch is working and pump not running you have a connection problem somewhere in the wiring.The wire from the relay and the switch join together , go through the fuse and then to the pump .
The FP will run off the OP switch even if the relay is disconnected if wiring is good

Popular wrong belief.
Switch is there solely to supply power to pump as backup to relay if it fails. If the OP switch cuts out at the set 4psi you still have the pump relay supplying power so the engine will continue to run.

Starting is different however.
The ECM has to see the OP switch ( over 4 psi ) come on line before it will fire the injectors

 

That's what it is...wasn't sure, that's why I put "I believe". It is at starting looking for pressure then...I thought it had something to do with the oil pressure switch :-p