Thread: fuel pump no prime

I just finished my det swap in my 96 sedan(sentra)

I bypassed the neutral safety switch, the starter kicks in and engine cranks, everything is good except the fuel pump.

When the key switch is on, the fuel pump does not prime.

The black/pink wire on one of the three underdash plugs is one of the fuel pump relay wires, and if i touch it with a test light or ground that wire, the fuel pump will kick on and stay on as long as i have it grounded. i know the pump should kick off at a certain pressure and i want the pump to work properly as it should with the key switch, so do you all have any suggestions as to what it could be?

btw, the pump is walbro 255 and known to be good(obviously good, you can ground that black/pink wire and the pump kicks on strong)

The fuel pump doesn't shut off at a certain pressure, it runs for 2 seconds for priming, otherwise it stays on when the engine is running.
It will stay on even with the key off?

no, it does nothing when key is on. Even with the key off, i can ground that black/pink wire and it will kick on and stay on.

sorry, i didnt mean to say it kicks off lol. Anyways, what do you think?

I had this happen on engine swaps when I forgot to ground both ECU grounds that bolt to the intake manifold. Double-check that they're secured and that the engine has good ground connections as well.

I meant, if you ground that black/pink wire with the key off does the fuel pump still run? And yes, triple check EVERY single ground.

i don't get why your fuel pump turns on when you ground one of the relay wires. isn't the fuel pump switched, not always hot? i know i had an issue one time with the fuel pump not working (properly). the fuel pump turned on and stayed on when i didn't screw on the ECU harness connector tight enough. in any case what you should do is pull the plug connector off the fuel pump and probe with your test light from there to see if it's getting voltage with the ignition at ON.

I believe that wire he's grounding is the signal wire from the ECU to the fuel pump relay. The ECU will ground the relay which will in turn supply voltage to the fuel pump.

yes the wire im talking about is pin 8 fuel pump relay. This stupid car is a disaster lol. I have never had so many issues with any other car.

Im going to check the plug itself...maybe the prong is bent or broken....anythings possible i guess.

did you make sure both ECU grounds were good and supplied to the intake manifold?

So what happened with this?