fuel pump troubleshooting

[jasond29]

I am just confirming that I might have an issue. According to the wiring diagram the fuel pump has a 25amp fuse and the fuel pump relay. The fuse is for the power side of the relay so I would assume that removing the fuse would prevent the fuel pump from getting power. That is not the case. I remove the fuse and the pump still activates. Is that normal? Is there some weird wiring that is not listed in the manual diagrams?

Thanks for any input.

-Jason

[dave6666]

Possibilities:

You removed the wrong fuse.
The relay is corrupted inside and the coil circuit is powering the load circuit.
The relay base is corrupted inside the base housing and there are wires supplying power to each other that shouldn't be.
If the main 25A fuse is up in the PDC the network of power busses in it could be corrupted and be bypassing or back feeding the fuse.
Your car has some aftermarket relay somewhere.

Tests:

Pull the 25A fuse and the fuel pump relay and then try both sides of the fuse socket to ground with a voltmeter. There should be power to one side only with the fuse and relay out.

Put the fuse back in and check power at both of the relay pump terminals 12V+ in and pump power out. There should be power to just the 12V+ in terminal.


If you have power where you shouldn't you may have something melted or shorted.

[jasond29]

awesome, thanks dave, will give those troubleshooting tips a shot.

[jasond29]

ok, so turns out the repair manual I have is for 98 and my car is a 2000. I was removing the wrong fuse. That actually brings up a new question. The top fuse "PCM fuse" 10 amp, what is that actually for?

[dave6666]

I would suspect that the PCM fuse is the main power to the PCM, possibly the ASD relay as well. If you really want to know how important the PCM fuse is, pull it while the car is running. Or try starting the car without it. Just make sure you have a code reader handy for the aftermath.........

[ellowviper]

Pulling the fuse in my 01 GTS does nothing for the fuel pump...it still activates key-on. I have to pull the actual relay by the amp in the rear to disable the fuel pump. I never researched it beyond that.