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AZ_HUNTER, GM World Class Tech
Category: Chevy
Satisfied Customers: 401
Experience:  16 years GM Tech, ASE Master Certified
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1994 Chevy: silverado..pickup..12V..power up the Fuel Pump

Resolved Question:

My 1994 Chevy 1500 350hp silverado pickup will not start. I cannot hear the fuel pump turn on, and I have a purple, black with white stripe, and grey wire going up into the fuel pump. Which wire is supposed to have 12V to power up the Fuel Pump? According to a manual, I put 12V to the terminal identification under the dash position "G", while ignition key off, I still could not hear the Fuel Pump come on. I've checked the Fuel pump Fuse under the hood, and it is good, although when ignition key is on or off, there is no voltage on this fuse. Please help on assisting troubleshooting efforts, as I believe it's a lack of power to the fuel pump issue.
Submitted: 8 years ago.
Category: Chevy
Expert:  AZ_HUNTER replied 8 years ago.

Hello and welcome to Just Answer.


The power lead to the fuel pump is the grey wire. the ground is the black wire. Connect the 12V test lamp to the battery 1st to make sure the test lamp is good. If test lamp is good, hook the clamp end to ground (I like to use a long piece of wire connected at the battery ground so that I am sure that I have a good ground) and the other end of the tester connected at the grey wire. Turn the key to the on position and the test lamp should light for 3-5 seconds and go out. This will tell you wether or not you have power at the fuel pump.

Customer: replied 8 years ago.
I do not have a lamp, but I do have a multi volt meter that measures voltage. What should the voltage be, and for how long will the voltage be applied until it goes off?
Expert:  AZ_HUNTER replied 8 years ago.
That will work. The voltage should be the same as the battery voltage, approx 12v. Verify the meter is working properly by first hooking it up to the battery. The voltage at the grey wire should be the same as the battery for 3-5 seconds. You could hook up the possitive lead to the grey wire and the negative lead to the black wire at the fuel pump connection.
Customer: replied 8 years ago.
I have checked for voltage on the grey lead, but I cannot see any voltage. Any ideas as too what check next? Should I put a temporary 12V wire lead to the grey wire, and check if the fuel pump at minimum comes on? Could it be the fuel pump relay?
Expert:  AZ_HUNTER replied 8 years ago.
Yes it could be the fuel pump relay. I would add power at the grey wire and see if the pump powers up. Does your manual tell you where the fuel pump relay is located?
Customer: replied 8 years ago.
Yes the book does locate the fuel pump relay. Any idea where I might want to apply 12Volts to the fuel pump relay? what lead on the relay that will apply voltage to the grey lead that goes up to the fuel pump?
Expert:  AZ_HUNTER replied 8 years ago.

I do not have that information here with me at home, but there should be one wire that is always hot (12v) and another that will turn hot with the key turned on. I can get you more information when I can get my hands on a manual at home. If there are wiring schematics in your manual, there should be one on the wiring for the fuel system.

If you can see the wiring at the back of the relay, you can look for the grey wire.

Customer: replied 8 years ago.
OK. Will the grey wire on the relay have 12Volts for about 3 to 5 seconds when the key comes on, or will it be a constant 12Volts when the key ignition is on? Thanks for Your help!!
Expert:  AZ_HUNTER replied 8 years ago.
It will just be for 3-5 seconds. I think, if my memory serves me correctly, the constant power at the relay is red, but I am not absolutly positive (been awhile).
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