Turn key on and the fuel pump does not turn on

1994 GMC SIERRA

200,000 MILES • 5.7L • V8 • 4WD • AUTOMATIC

BAILEY BRASSARD

MEMBER
2 POSTS

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?

Apr 15, 2020 at 2:43 PM

DANNY L

✓Experienced 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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Apr 15, 2020 at 4:07 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.

Apr 15, 2020 at 5:03 PM

STRAILER

✓Experienced Mechanic
55,319 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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Apr 16, 2020 at 3:47 AM