Fuel pump relay?

Tiny
FABIAN19720
  • MEMBER
  • 1987 CHEVROLET SILVERADO
  • 89,000 MILES
I just replaced fuel pump cause had no power lucky I did cause strainer was bad but still no power to it but when I run jumper from fuel relay to 12 volts the pump works it does have dual tanks but the passenger side doesnt work there is not any fuse links on power wire by battery only by alternator and down by starter both are good check fuel relay and its good. Did separate the fuse box from outer but dont see any fuse links there either. Have any idea on where else I can check?

Not really sure if I check it and I dont have voltage there where do I go from there as I already tried changing ecm and no difference
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Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
WRENCHER1
  • MEMBER
Yes, before we waste a bunch of time looking elsewhere, we need to know the pump isn't part of the problem and that fuel supply is the only problem.
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Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
KHLOW2008
  • EXPERT
At the ECM, check terminal A1 for battery voltage with ignition turned on. This would only last a couple of seconds as the fuel pump primes. Crank the engine and if battery voltage is available, you have a broken connection between the ECM and the relay. There are 5 terminals for the fuel pump relay, do you have battery voltage at the Tan/White wire? If no, check the oil pressure switch.

Here is a guide to help you test the relay

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Please let us know what you find.

Cheers
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+8
Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
WOLFE1
  • MEMBER
Alright i, ll check and get back with you tuesday as it isn, t at my house.
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Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
FABIAN19720
  • MEMBER
Do u have the wiring diagram for the fuel system in my truck that u can post for me
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+4
Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
WRENCHER1
  • MEMBER
While your in the area, make sure the tension on the contacts of the harness plug are sufficient to make good solid contact. They have a known problem with them. You can use a pick to bend them a little to make them tighter.
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Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
KHLOW2008
  • EXPERT
Here you are. They are too small so I split them up. See if you can print them out and join together for a clearer picture.
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+2
Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
WOLFE1
  • MEMBER
Will do.
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Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
FABIAN19720
  • MEMBER
Ok on my truck on same bracket as fuel relay theres another relay there with different number but nothing plugged into it do u have any idea on what its there for
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Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
FABIAN19720
  • MEMBER
I read on another website that some trucks cam out with a 20 second relay for harder starting trucks not sure if thats what it is or not
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Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
KHLOW2008
  • EXPERT
These are what I have for the relay.

Sorry I do not know anything about the 20 seconds relay.
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Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
FABIAN19720
  • MEMBER
Thanks! I will get the number off the relay thats next to fuel relay. Gonna go out in little while to see if I can trace down my loss voltage will keep u updated
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+1
Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
AFICIO
  • MEMBER
Hot fuel is actually a small pcb inside a black plastic box located on the steering column most likely the right side just above the brake, it is usually found on pickups with the 7.4 and is used to prevent vapor lock, it runs I thought 15 sec. I have had them both stop the fuel pump as well as allow the vehicle to run with the key off because one shorted.I have found newer trucks to have them also behind the glove box. In case you are looking in a wrecking yard, I believe dealer price is around 80.00. Good luck.
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Tuesday, July 7th, 2020 AT 1:42 PM (Merged)
Tiny
KEN
  • ADMIN
Great addition to this thread! Please feel free to help out whenever you are on the site :)

Cheers, Ken
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Tuesday, July 7th, 2020 AT 1:42 PM (Merged)

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