I have a n 07 Lucerne every so often the fuel pump will run for 30-40 seconds then cycle normally. When I say every so often, it happened about a month ago then just started doing it again the last few days. Am I looking at a faulty pressure sensor or is the pump getting tired.

What do you mean by...."cycle normally"? The pump should run all the time the engine is running.

All fuel injection systems tank pump only cycle on demand to maintain rail pressure, normally you will hear it for a few second when you turn on the key to pressurize the rails then it will cycle as needed. Mine will off an on stay running for much longer cycles, trying to figure out if it is a pressure sensor issue or is the a pump issue.

Phil

The PCM will ground the fuel pump relay for about 2 seconds or until it sees a crank signal. If the PCM does not see a crank signal it will cease the ground for the fuel pump relay. Your relay may have sticky points. Switch it with another relay or just replace it with new and see what you get.

Thanks will swap in a new one in the AM.

Phil

Yes, the relay seems like a plausible explanation.....Wouldn't be the pump......and there is no sensor for fuel pressure, per se.....

I'd be curious what the fuel pressure is doing while this is happening.

I popped a new relay seems to have cured it, will keep an ear on it!

Thanks

Phil

Thanks for the relay tip! I took 4-5 local trips and decided to look at the fuel usage my average fuel mileage it usually shows 22.5 it was down to 16.3. Looks as if I have been dumping extra fuel. Much of my driving is semi rural roads and moderate highway, so I do pretty good on gas about the same as my PA. I will chime in in a few days with a follow up.

Phil

Thanks for letting us know what might have fixed it!

I have to say this doesn't make sense to me. The relay would have no effect on how much fuel is getting dumped anywhere . . . except to allow or deny fuel getting anywhere at all.