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Old 04-10-2017, 07:05 AM   #1
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Join Date: Apr 2017
Location: Mesa, Az.
Posts: 6
Angry Need help on 93 c1500 fuel pump won't turn on.

IDK the wiring diagram but I do know that it's linked to the oil pressure sender I'm order to power the relay but need help if anyone can help on what wires are powered & which one goes to the ecm & which one runs to turn on the fuel pump, thanks.
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Old 04-10-2017, 01:56 PM   #2
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Join Date: May 2004
Location: Minnesota
Posts: 4,450
Re: Need help on 93 c1500 fuel pump won't turn on.

Welcome to the board!

Fuel pump relay wire colors 1993 C/K gasoline engine:
Red (circuit 490) ALDL connector terminal G(for early years) or Test lead
Dark Green with white tracer (circuit465) From PCM (computer) this controls the relay
Gray (circuit 120) to fuel pump - earlier TBI trucks had tan with white tracer
Black with white tracer (circuit 450) Ground to engine ground G109 (by T-stat)
Orange (circuit 440) power from fusible link at firewall junction block

The ECM controls the fuel pump relay.
The truck has a fuel pump relay that supplies power to the fuel pump when:
- Anytime the ECM receives a distributor reference pulse. (Engine running / engine cranking)
- The key is turned on engine not cranking relay applied for 2 to 20 seconds.

When the engine has oil pressure a redundant circuit supplies power to the fuel pump. This circuit goes through an oil pressure sensor/sender. This circuit is independent of the fuel pump relay.
For those of you that are wondering why you are not getting replies to your thread:
Did you give the model, year, engine, fuel system type, and transmission information?
If it is modified from what came stock from the factory, let us know that too.
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