Turn key on and the fuel pump does not turn on

BAILEY BRASSARD

MEMBER
1994 GMC SIERRA
5.7L
V8
4WD
AUTOMATIC
200,000 MILES

However, I can hook direct power to it and it comes on, yet the 2 injectors won't work. I have changed harness, fuel pump, have oil pressure. Why won't my pump turn on from key?

Wednesday, April 15th, 2020 AT 9:43 PM

3 Replies

DANNY L

MECHANIC
5,648 POSTS

Hello, I'm Danny.

Sounds like you might be having an issue with the fuel pump relay.It's mounted on the right side of the firewall.Here is a tutorial on how to test a relay:

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

I've attached a picture of the location of the relay on your truck.Hope this helps and thanks for using 2CarPros.

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Wednesday, April 15th, 2020 AT 11:07 PM

BAILEY BRASSARD

MEMBER
2 POSTS

Sorry Danny, but my truck has a pump relay on the passenger side firewall. And I have changed and tested it.

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Thursday, April 16th, 2020 AT 12:03 AM

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

Okay, Lets see if the PCM is getting power and ground. here is a guide to help with the testing and the engine and computer wiring diagrams so you can see which wires to test and how the system works. Make sure you test the fusible link.

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (below). Please run this test and get back to us.

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