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Fuel pump issues

hello, my fuel pump will not turn on when the ignition key is in on position. relays and fuses are fine. the thing is when it decides to work, truck starts and runs great. it will be ok for a day or 10 days. park it in the driveway but the pump will not activate so it will not start the next morning. this has happened 3 times in the past month. please help. thank you! paul

Sounds like a failing fuel pump to me. Replace it. (The bearings are going and sometimes it is not strong enough to start turning. You can probably get a jump start from a running car to boost the voltage enough for the fuel pump to start running. However, it’s going to fail altogether soon.)

How do you know the fuel pump isn’t running?

The next time you think the fuel pump isn’t working, get a rubber mallet and bang on the bottom of the gas tank and then try starting the engine. If the engine starts it’s time to have the fuel pump assembly replaced.

FYI. It’s much easier to tilt/remove the truck box than it is to drop the fuel tank when replacing the fuel pump.


no sound from the pump when the key is turned to the on position

believe me… i hit the thing. unbolt the bed? thats alternative thinking for sure but it makes sense if its possible. ill look into it.

That was another question I had. Can fuel pump function sporadically? I thought when they go they go.

As a test, for those times when you don’t hear the fuel pump run, you might want to find out if the cause is because the fuel pump isn’t getting power, or if it is, but, not running. How could you do this? Pull the relay which powers the fuel pump, and connect a hot wire (12 volts) to the wire going to the fuel pump. If the fuel pump then runs, the fault may be lack of energizing power to fuel pump relay.

its getting power. all the wires look good. other than that i have no codes showing on my scanner. I did, but it was an o2 sensor b1/s2 and fixed that. the more i get into this i think its time to replace the fuel pump. I figure if have to get to it and test continuity at the pump thats 99% of the battle i was trying to avoid. its cold in wyoming.

You say the pump is getting power. How did you confirm that? Test light back at the fuel pump connector?

If the test light indicates power at the pump, you then need to check the ground circuit. The ground for the fuel pump module is actually near the battery.

Yeah, as a general rule, electric motors are harder to start than to keep moving once started. If I recall correctly, there are a zillion variations on the basic electric motor, but what most of them seem to have in common is that getting the rotor moving is a problem. Also, I believe that most motors require electricity to be applied to the rotating part of the motor. When they age, the contacts between the rotor and the “brushes” can become unreliable. If the motor stops in just the wrong place there may not be any contact between the power source and the rotor when you try to start the motor again.

ohmmeter. managed to get the plug off last night and test. reconnected the plug. this morning out of frustration pushed the crap out of the connector as a last ditch effort to avoid dropping money on a fuel pump and it started. i dont trust it as far as i can throw it.

Ohmmeter? Do you mean voltmeter?

You can’t check for power with an ohmmeter, an ohmmeter checks for resistance.

youre right, voltmeter… my neighbor came over and checked the wires for voltage up stream. couldnt get to the fuel pump.