Quote:
Originally Posted by Jetex
I have not got a wiring diagram specific for your model. A typical GM system works like this :-
Turn ignition on. Pump relay gets energized via ECM and contacts on relay feed power to pump. Pump runs approx. 3 seconds, primes fuel rail and relay switches off. Crank engine and engine starts. Engine runs and contacts on oil pressure switch close which now feeds power to pump. This is a safety interlock to prevent the engine running with no oil pressure. In the GM drawing I have, the pump relay can be removed with the engine running and the the engine will continue to run. The relay is only used to prime the fuel rail.
Maybe your oil pressure sensor has defective contacts?
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Thanks for adding the extra help there, my Nissan is like the way I told him. I did look at my haynes manual for my buick and it is exactly like you said with the oil pressure switch. But I'm still going with the fuel pump relay seeing how he said it's when he turns his key on half the time it works and half the time it don't. Either way it should turn on when he cuts the car on. So I'm still thinking something in his ignition switch or his fuel pump relay.