1978 280z fuel pump runs constantly

[Lyttek]

New problem just developed, haven't had time to anything but basic troubleshooting. Car has been running fine.

Drove, parked, shut car off. Heard fuel pump running, gauge on dash shows a discharge (red light). Pulled negative cable from battery, pump stops. Put cable back on, I can hear the fuel pump relay click, but pump doesn't run.

Turn key on, pump comes on for "priming" and never shuts off; have to pull battery cable again.

One thing I tried but don't know if it holds true for this car like some others: started car, runs fine. Pulled battery cable while running, car dies. (should it not keep running if alternator is fine?)

It's going to be a couple of days before I get a chance to delve into, so thought I'd start researching ahead of then.

TIA

[Lyttek]

Just thought I'd post an update: the alternator was bad. Unsure why that would affect the fuel pump, but all's well on that front.

[TomoHawk]

The fuel pump power is probably switched by a relay. Your relay must be stuck ON.

Edited December 8, 2011 by TomoHawk

[sblake01]

Unlike the 75, 76, and 77, the alternator is part of the fuel pump control system on a 78. Whatever the problem your alternator had was apparently causing it to send the signal that ordinarily would require the ignition switch to be in the on position.