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91' F150 351 / Fuel pump relay issue

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91' F150 351 / Fuel pump relay issue

Old 09-02-2015, 11:06 PM
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Default 91' F150 351 / Fuel pump relay issue

Hi all,

I'm in need of some help. I've just purchased a 1991 F150 with the 351 windsor. The seller has told me about an issue with the fuel pump relay getting hot and the fuel pump then cutting out.

Test driving the truck confirmed there is some issue, it would begin to cough and splutter and i could not accelerate. I would have to turn the truck off then on to reset the issue and it would run for another 10mins before happening again. After turning the truck off and on the time between the truck playing up would reduce each time.

One time it would not restart and I could not hear the fuel pump priming the system (bled the fuel rail to confirm it wasn't at pressure). After "wigling" the relay a few times it started to work again.

There is a fare amount of dodgy wiring all over the place with this truck. I'm wondering if anyone has the wiring diagram of the fuel pump system and or knows what size/type of relay controls the fuel pump? (whats there at the moment looks aftermarket and damaged from what appears to be overheating).

fyi - I've purchased original shop manuals on ebay but wont see them for a couple weeks. I was hoping to get stuck into troubleshooting this weekend.

Thanks in advance for any help!!
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Old 09-05-2015, 04:02 PM
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It should be a usual black square relay in the power distribution box. Try swapping in the one from air conditioning.
If another relay is also getting hot, I would think it's been rewired with too much power going through.
A lot of them are set up to have 12 volts for the 2 second prime then 6.5 volts for constant run. I just remember reading that somewhere, but you could see how it might overheat a relay.
You can also turn the power distribution box over and remove the bottom to see if there are any wiring problems underneath there.
That's assuming your truck has a power distribution box - beside the air cleaner box ?
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Old 09-02-2017, 11:21 AM
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hi
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Old 05-25-2018, 05:11 AM
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Originally Posted by puke22 View Post
Hi all,

I'm in need of some help. I've just purchased a 1991 F150 with the 351 windsor. The seller has told me about an issue with the fuel pump relay getting hot and the fuel pump then cutting out.

Test driving the truck confirmed there is some issue, it would begin to cough and splutter and i could not accelerate. I would have to turn the truck off then on to reset the issue and it would run for another 10mins before happening again. After turning the truck off and on the time between the truck playing up would reduce each time.

One time it would not restart and I could not hear the fuel pump priming the system (bled the fuel rail to confirm it wasn't at pressure). After "wigling" the relay a few times it started to work again.

There is a fare amount of dodgy wiring all over the place with this truck. I'm wondering if anyone has the wiring diagram of the fuel pump system and or knows what size/type of relay controls the fuel pump? (whats there at the moment looks aftermarket and damaged from what appears to be overheating).

fyi - I've purchased original shop manuals on ebay but wont see them for a couple weeks. I was hoping to get stuck into troubleshooting this weekend.

Thanks in advance for any help!!
The fuel pump could be shorting out or going bad causing the problem or could be as simple as the fuel pump pick up filter being clogged up causing the pump to work harder
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Old 05-25-2018, 10:40 AM
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This thread is 3 years old. If he hasn't fixed it by now, he probably sold or scrapped it.
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Old 05-26-2018, 10:36 AM
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Originally Posted by Steve83 View Post
This thread is 3 years old. If he hasn't fixed it by now, he probably sold or scrapped it.
Ha, guess I need to pay more attention when I am drinking lol
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Old 06-07-2018, 05:23 AM
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Heck drink one for me while you're at it I've been dealing with this 95 F-150 with an inline 6 in dual tanks for the past couple of months it was my father's truck who is recently deceased and I would really like to keep it going whenever I replace the fuel pump because of bad gas and it being varnished up I haven't been able to drive it anymore I'm not getting the correct voltage to the pump at best I might give it to start for a second I read where people were saying not to use a voltmeter to use a test light with a voltmeter the best I got was 9 1/2 volts. I would really like for it to run right without having to dike the wires on it but I'm about ready to the voltage to the pump is supposed to be 12 volts continuously? What about the sending unit what volts should it be getting?My inertia switch isn't tripped I don't know what's going on with this thing it's really starting to frustrate me
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Old 06-08-2018, 12:41 PM
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Originally Posted by Jace Blain Rice View Post
Heck drink one for me while you're at it I've been dealing with this 95 F-150 with an inline 6 in dual tanks for the past couple of months it was my father's truck who is recently deceased and I would really like to keep it going whenever I replace the fuel pump because of bad gas and it being varnished up I haven't been able to drive it anymore I'm not getting the correct voltage to the pump at best I might give it to start for a second I read where people were saying not to use a voltmeter to use a test light with a voltmeter the best I got was 9 1/2 volts. I would really like for it to run right without having to dike the wires on it but I'm about ready to the voltage to the pump is supposed to be 12 volts continuously? What about the sending unit what volts should it be getting?My inertia switch isn't tripped I don't know what's going on with this thing it's really starting to frustrate me
For starters you can check to see if the power wire itself is shorted out somewhere, may have a bad spot or rusted somewhere or both. You can pull the wire from both ends and test it to ground to see if it is grounded. Also you can run a new wire from both ends, as a test, and see if the truck stays running. I havent messed with them very much. Good Luck, let me know. I can ask one of the guys here at work that works on the Ford vehicles alot.
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Old 09-20-2018, 03:01 AM
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Wrong thread. Delete post.

Last edited by Taurus4Life; 09-20-2018 at 03:04 AM.
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