Fuel Pump Relay

Tiny
RIGHTTOO
  • MEMBER
  • 2 POSTS
  • 1994 CHEVROLET TRUCK
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
My truck stalled on me and I was not able to get it running agian. I realized it was a fuel problem so I replaced the pump, relay, and fuse, my pump is still not turning on when I turn the key.
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Sunday, November 4th, 2018 AT 12:35 PM (Merged)
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,749 POSTS
Check for power at the gray wire at the relay when you turn the key on and if you have power for 2 seconds then the gray wire must be broken from there to the tank.
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Sunday, November 4th, 2018 AT 12:35 PM (Merged)
Tiny
BOBFRANK
  • MEMBER
  • 6 POSTS
No tank was full of rust and stuff, so fuel pump burnt up. Cleaned tank out, new pump and filter and ever since it has done this. Have also put a computer in it. Any suggestions? THANKS
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Sunday, November 4th, 2018 AT 12:35 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
The fuel pump should come On for 2secs only when the computer energizes the fuel pump relay. If not its coming from the computer relay driver-

Try this use starting fluid thru the throttle body and see what happens-


https://www.2carpros.com/forum/automotive_pictures/12900_oil_sending_unit_and_fuel_pump_circuit_81.gif

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Sunday, November 4th, 2018 AT 12:35 PM (Merged)
Tiny
BOWTIE BABY
  • MEMBER
  • 101 POSTS
How many wires are on the oil pressure switch? It could have a safety feature so if you lose oil pressure the fuel pump will shut off, Try replacing the oil presure switch again. It could be faulty out of the box.
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Sunday, November 4th, 2018 AT 12:35 PM (Merged)
Tiny
RIGHTTOO
  • MEMBER
  • 2 POSTS
When I turn the key on and test the fuel pump fuse with a test light. It shows no power on either side. Iam wondering if it is a computer related problem or a short in the wiring. But if I unplug the wiring harness from the sending unit and test the wires there the center wire has power. Also when I turn the key on the pump makes a one click sound but does"nt fully kick on. And if I dump fuel down the TBI it will start. Please give me your input on this if you can. It is not to often that I can"t figure something out on my own, but this one has me stumped thank you
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Sunday, November 4th, 2018 AT 12:35 PM (Merged)
Tiny
BOBFRANK
  • MEMBER
  • 6 POSTS
Tried that, put a oil pressure switch from another truck and it still does not shut off. The ops has 3 wires. Checked for voltage at fuel pump fuse under hood and check lite is very brite on one side and then dimmer on other side. Checked fuse on the other truck and check lite only lites up on one side while fuel pump is pumping. Can hear the relay click in and then something else clicks. From listening to the other truck, the other click is when the fuel pump is getting ready to shut off. Then something clicks and then the relay clicks. Weird.
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Sunday, November 4th, 2018 AT 12:35 PM (Merged)
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,749 POSTS
With key on you should have power at one termianl of relay(orange wire) dark green should pule a ground for 2 seconds when key is turned on which will energize the relay and send power to the gray wire. What are we missing?
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Sunday, November 4th, 2018 AT 12:35 PM (Merged)
Tiny
BOWTIE BABY
  • MEMBER
  • 101 POSTS
Have you replaced or switched the relay with the other truck. If it sounds funny and power is in different places than the other truck it may be a bad relay bad.
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Sunday, November 4th, 2018 AT 12:35 PM (Merged)
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,749 POSTS
Whn you turn the lkey to run position with truck off is the check engine light illuminated? It should be, if not check inj fuse
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+1
Sunday, November 4th, 2018 AT 12:35 PM (Merged)

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