Fuel Pump Problem?

[lazabby]

I drove my car a few das ago. Today I got into my car to move it and it wouldn't start. Turns over fine. I have a fuel pressure gauge on a fuel line and I have no fuel pressure. I don't hear the pump priming when I turn the key. I checked the #7 fuse and it looks good. Before I tear into the trunk to get to the fuel pump (original pump) anything else I should check?

[David T]

I drove my car a few das ago. Today I got into my car to move it and it wouldn't start. Turns over fine. I have a fuel pressure gauge on a fuel line and I have no fuel pressure. I don't hear the pump priming when I turn the key. I checked the #7 fuse and it looks good. Before I tear into the trunk to get to the fuel pump (original pump) anything else I should check?

Make sure you are not out of gas and cycle the plunger on the inertia switch up and down. The jumper the RPM relay and see if that gets the pump to run.

[Bitsyncmaster]

You jumper the brown wire to the white/purple wire on the RPM relay socket to "jumper the RPM relay". That will bypass the RPM relay which will power the fuel pump.

[lazabby]

The inertia switch seemed to be ok but it might be a good idea for me to toggle it up and down as suggested. How much voltage should the pump be getting. I did put a volt meter on it (if I was doing it right) and wondered how much should be coming through.

[Bitsyncmaster]

The inertia switch seemed to be ok but it might be a good idea for me to toggle it up and down as suggested. How much voltage should the pump be getting. I did put a volt meter on it (if I was doing it right) and wondered how much should be coming through.

Typical voltage loss from the harness and connections is less than one volt. So with the engine running (has to be for the RPM relay) your battery voltage should be above 13 volts and your pump voltage across the two terminals should not be below 12 volts. I did run a test on one fuel pump and it could put out 75 PSI down to 8 volts across it.

[Timebender]

Is it a bad idea to just jumper that and keep it that way, as the inertia switch does the same thing in shutting off the fuel pump in an accident, or when jumped, the fuel pump runs even with the ignition off?

[DMCMW Dave]

Is it a bad idea to just jumper that and keep it that way, as the inertia switch does the same thing in shutting off the fuel pump in an accident, or when jumped, the fuel pump runs even with the ignition off?

The intent is that it shuts off the fuel pump in the event of a crash that doesn't kill the engine. It interrupts ground, so it will not make the pump run all the time.

Keep in mind that 99% of the time you crash a car, the engine stops (especially in manual trans cars), and once the engine stops the RPM relay kills the pump too.

But there is that 1%. . . . (See recent Y-tube video where a kit rolls daddy's new Lexus and the engine keeps running. And then they roll the car back onto the wheels........)

[sdg3205]

When fuel pumps randomly stop its often the rpm relay giving up the ghost or a non-white dot inertia switch melting.

[David T]

When fuel pumps randomly stop its often the rpm relay giving up the ghost or a non-white dot inertia switch melting.

The inertia switch and the RPM relay do the same thing but for different reasons. They both will shut down the fuel pump. The inertia switch is supposed to shut the pump down in a crash, the RPM relay is supposed to shut the pump off if the motor is not running. You can do it also by shutting off the ignition switch BUT! If you jumper the RPM relay you are powering the pump EVEN IF THE IGNITION SWITCH IS OFF! Jumpering these switches is to be considered for trouble-shooting or EMERGENCY purposes ONLY!

[lazabby]

I checked power to the pump. It looks like it's getting plenty of voltage so it looks like a bad fuel pump. I don't look forward to replacing it.:mad1:

[David T]

You must check power AND ground at the pump. If either is not there the pump won't run. If you have power and ground and you don't hear it running, you are correct, the pump is dead. Before ordering the pump you should take it all apart and see if you need anything else so you can order it all at once. No sense ordering the pump, waiting for it, and then finding out the boot is bad or the pick-up hose is no good and you have to place another order before you can put it all back together. Make sure your inertia switch has a splotch of white paint on it and it is mounted on the left side footwell, NOT the Lambda counter. Check fuse #7 to make sure it isn't melted out of the fuse box. While you are in the tank look for any contamination or debris on the bottom. If there is water in there you will see a bubble of it moving around on the bottom. Of course it should all get cleaned out.