1992 grand prix 3.1 fuel pump wont turn off.

[napoleankjj2006]

have 92 grand prix. this just started today but the fuel pump wont turn off by the keyt. i tried buying a new relay. dont work. i checked all the fuses just to make sure. known are blown. someone told me i could fuse the fuse blcok up find the wires going to the fuel pump fuse and hook a swicth to it.

is that a possibilty or what do i do

[CrazyHorst]

...I assume you are able to shut the car off...

I would think the usual components are : keyed switch, relay, and fuel pump. Not sure how the ECM is involved in a 1992 model. It is a possibility there could be some sort of unexpected voltage...in other words...if something had "shorted" into the fuel pump circuit.

I would say that a factory wiring manual is going to pay big dividends. You can certainly track this down via "brute force" which means following wires and taking apart everything else that's in the way until the circuit becomes clear to you....but that's usually pretty painful.

[napoleankjj2006]

let me correct what i typed originally.

the car will start and everything. wont die or stall.
its when u turnm the car off and have the keys in your hand, the fuel pump is still going until u pull the fuse out.
i replaced the relay , no change.

i was told i could go buy a toggle switch and hook into one of the wires going to the fuel pump fuse on the fuse block and turn the pump on and off that way. i wasnt sure if this was true or not.

[tblake]

You will not want to install a toggle switch. I hate when people do things like this to their cars. By the time you go through all the trouble for a toggle switch, you might as well trace down the problem. Not to mention you open up a whole new can of worms for problems with a toggle switch up to and including reliability/drivabilty issues, and possibly forgetting to turn it off causing a dead battery and a burned out pump.

I'm pretty sure in some older gm cars that the pump could be commanded two ways. Either by the pcm through the fuel pump relay, or else through the oil pressure sensor. During cranking, as soon as the oil pressure sensor senses proper oil pressure, it commands the fuel pump on. (I could be wrong).

Yank out your fuel pump relay, is the pump still running? If no, try and start your car. It may crank longer than normal as oil pressure builds up, but if my memory serves me correctly, after a few seconds, your car will start.

From there you can diagnose why your pump constantly runs through the relay socket whether it be that a wire is being grounded and commanding the relay on, or if the ECM's fuel pump relay driver circuit is shorted.

[napoleankjj2006]

when u pull the relay, it stays on.

[tblake]

Hmmmm, interesting. I will see if I can get a wiring diagram.

[napoleankjj2006]

the wiring diagram will still help me in the future but this morning , whne i put the fuse and the new relay back in, the pump was off until i started the car.

could itbe it just needed reseted over night?

[CrazyHorst]

Couple of issues.

Keep in mind that the relay has a circuit which energizes the coil.

Once the coil is energized, it pulls in the relay contacts.

The normally-open contacts are wired in series with the fuse block, in other words the contacts have the job of switching the relatively high amperage needed to run the fuel pump.

I like to think conceptually of the "signal" side of the circuit being the coil side of the circuit and the "power" side of the circuit being associated with the contacts.

So...in your case, if the signal/coil side of the circuit (likely coming from keyed switch or ECM) is ON all the time, no amount of relay changing is going to help because the relay is doing exactly what it is commanded to do. Pulling the fuse simply breaks the circuit on the power side of the circuit (while the relay is likely still in the same state).

To fix this problem you could do one of a couple things.

a) trace back and see if the keyed switch or ECM is in control of the fuel pump relay. I would suspect the keyed switch, personally, based on model year, without any official documentation.

b) manually "take control" of the relay by wiring the coil to a detented switch (one that maintains position ala the classic residential wall-switch although I am not suggesting using that particular switch) and then to a 12v source. Then you would have full manual control over the relay.