Mechanics

WHAT CAUSES FUEL PUMP TO FAIL ONLY AT START UP?

1992 Nissan Maxima • 140,000 miles

It's occurring more often. With ignition on the pressure builds up to 40psi, if it starts, pressure stays up (36.0psi) and the engine will run until it's turned off. If it fails to start, the pressure drops off and doesn't return for several attempts, or until I get tired of trying. Go out an hour later or the next day, it fires up. The regulator checks out, 36.0psi at idle 43.0psi throttle up. Disconnect vacuum pressure rises to 40psi. The resistance in the pump is 0.5, which is where it's supposed to be. Replaced the pump relay and checked all but one connector, E.F.I. Harness to the relay harness (F52-M36), I have no idea where that's located. When not starting, checked voltage through both pump and safety relays (11.8) in and out, connector at pump (11.8) either side of connector. I am at a loss. It doesn't seem like a short or bad pump, because it hasn't quit running yet, only has problem when starting. Any ideas? I have been searching forever on line for answers and haven't found a similar problem.
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Jacksonj
December 6, 2011.




Have you checked voltage while pressure drops?
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Tiny
Fixitmr
Dec 6, 2011.
I think you are chasing the wrong area. The fuel pump primes through the relay and then after the 2 second prime, it restarts when it see the reference signal for spark and injector pulse and that's where your problem may lie. See if you are losing spark and injector pulse when this happens.

Wrenchtech
Dec 7, 2011.

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