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Fuel pump wiring issue

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Old 05-04-2024, 04:01 AM
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Car: 87 iroc z
Engine: 5.7 350 tpi
Transmission: 700r4
Fuel pump wiring issue

Hey everyone! I'm new here. Working on a 87 iroc z 350tpi. Been trying to track down an electrical issues with the fuel pump, the fuel pump doesn't start when I turn the key to run, or when I turn it over. I've concluded that the fuses, are good, including the one by the battery, relays are good, brand new fuel pump, checked the wiring from the fuel pump back to where it reenters the car behind the seatbacks, and its good up till it runs under the base of the seats. Is there another switch or relay I'm missing? Any help would be greatly appreciated!!
Old 05-04-2024, 07:20 AM
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Re: Fuel pump wiring issue

Hi Yaboiafton, welcome to TGO

Figured I'd ask, because I didn't see it mentioned in your post;

Have you checked the connector under the rear seatbacks, where the wires pass through the body to get to the fuel tank?

Here is a thread with pics showing the connector ......

https://www.thirdgen.org/forums/elec...connector.html
Old 05-04-2024, 07:36 AM
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Car: 87 iroc z
Engine: 5.7 350 tpi
Transmission: 700r4
Re: Fuel pump wiring issue

Yes I did, it was pretty crusted with dirt which I carefully chipped off, and It has a new connector as the fuel pump came with another harness. A little more context on the issue, it just wouldn't start one day, figured out it was fuel related and got it towed home. Tried to start it the next day and it fires right up, I shut it off after a bit and she wouldn't start again🤔 since then I've been trying to track it down as it could be something simple like a loose ground or something like that, but I don't know where else to look.
Old 05-04-2024, 08:51 AM
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Re: Fuel pump wiring issue

For diagnostic purposes, power can be fed to the pump via the blue wire at the relay, or through the "G" terminal on the ALDL connector under the dash. However, feeding through the ALDL requires that the pump relay and its wiring are fully intact.

You can also apply power and ground directly at the rear floor connector, C315, to see if the pump is intact.
Old 05-04-2024, 10:43 AM
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Car: 1986 IROC Z
Engine: 5.0 TPI
Transmission: 700R4
Axle/Gears: 3.23 Posi
Re: Fuel pump wiring issue

Originally Posted by Vader
...You can also apply power and ground directly at the rear floor connector, C315, to see if the pump is intact.
^^^^This.

Or use a test light (don't rely on a multimeter reading) at this connector to see if 12v is present when attempting to start the engine.



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