Fuel pump kicking on when motor off?
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Junior Member
Joined: Feb 2004
Posts: 9
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Fuel pump kicking on when motor off?
1990 f150
300 I6
dual tanks
Well, a few weeks ago I stopped and got gas, came out and i had a dead battery. No big deal because it was a 4 year old battery. So I took a battery out of an old vehicle I had and ran that battery for a week. That battery died too. So it is possible that I just had 2 old batteries. The alternator is only about 2 months old. I checked the battery a few days before it died and it showed 12 and with the motor running the alternator shows 14. Well, yesterday I went out to check the voltage and when I shut the door, I thought I heard a fuel pump hum like it does when you first start the truck and kick back off. I shut the door again and heard it again. I shut it several more times and it didn't do it any more. Then sitting in the truck, I heard it kick on for just a second and quit. Any ideas? Every time the battery has died, I have been on the front tank, so when I parked it at work today, I switched to the back tank . ANy ideas?
Thanks.
300 I6
dual tanks
Well, a few weeks ago I stopped and got gas, came out and i had a dead battery. No big deal because it was a 4 year old battery. So I took a battery out of an old vehicle I had and ran that battery for a week. That battery died too. So it is possible that I just had 2 old batteries. The alternator is only about 2 months old. I checked the battery a few days before it died and it showed 12 and with the motor running the alternator shows 14. Well, yesterday I went out to check the voltage and when I shut the door, I thought I heard a fuel pump hum like it does when you first start the truck and kick back off. I shut the door again and heard it again. I shut it several more times and it didn't do it any more. Then sitting in the truck, I heard it kick on for just a second and quit. Any ideas? Every time the battery has died, I have been on the front tank, so when I parked it at work today, I switched to the back tank . ANy ideas?
Thanks.
Member
Joined: Jan 2004
Posts: 15
Likes: 0
From: Greater Austin, Texas
I suspect the fuel pump relay. If there is one for the back and one for the front, just swap them and see if the problem moves to the back. The computer tells the fuel pump relay when to run the pump but it does that by grounding the relay. So the wire from the cpu to the relay could be shorting to ground as well, but check the relay first.
The relay(s) should be on the driver's inner fender and it is (they are) green.
The relay(s) should be on the driver's inner fender and it is (they are) green.
Thread Starter
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Junior Member
Joined: Feb 2004
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Yep,
I went back and slammed the hood, heard the pump. Tap on the housing that the relay is in, the fuel pump kicks on. Also, there is a ground wire disconnected. After fooling with it, the pump quit coming on. I haven't connected the wire yet since I'm at work. I'll probably connect the wire and just buy a new relay to play it safe. Could this have caused my truck to miss every once in awhile when driving and mess up my gas mileage??
Thanks
I went back and slammed the hood, heard the pump. Tap on the housing that the relay is in, the fuel pump kicks on. Also, there is a ground wire disconnected. After fooling with it, the pump quit coming on. I haven't connected the wire yet since I'm at work. I'll probably connect the wire and just buy a new relay to play it safe. Could this have caused my truck to miss every once in awhile when driving and mess up my gas mileage??
Thanks
Member
Joined: Jan 2004
Posts: 15
Likes: 0
From: Greater Austin, Texas
Well, you never know, but I doubt it unless there is another problem somewhere that this made worse. As long as the fuel pressure regulator is working properly, the "extra" fuel (which would be all of it when the engine is off) is just sent back to the tank.
