Fuel pump

1990 CHEVROLET CORVETTE
105,000 MILES • 5.7L • V8 • 2WD • AUTOMATIC
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MIKETHOMAS78
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Car was running turned it off. once you start it again and no power to fuel pump. and I am now getting power for the fuel gauge wire is now powered. what would cause that?
Sep 19, 2019 at 11:41 AM
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94 TRANSAM
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Hi, welcome to 2CarPros.

I am sorry but I didn't quite follow what you were saying. Could you possibly re-type your problem with as much detail as possible.

Thank you Rich
Sep 19, 2019 at 1:59 PM
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MIKETHOMAS78
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What would cause the car to have power on the negative for fuel gauge?
Sep 20, 2019 at 12:11 PM
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MIKETHOMAS78
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  • 3 POSTS
Corvette sending unit 3 wires black grey purple car was running shut off. now I'm getting power through the purple wire from the fuel gauge power should be on the gray wire both black and purple should be ground.
Sep 20, 2019 at 12:13 PM
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94 TRANSAM
  • ✓Experienced Mechanic
  • 680 POSTS
Black is ground
gray is fuel pump
purple is sending unit

The sending unit is on a 12 volt circuit with a variable resistor at the end (the sending unit) if the key is on you will have a voltage reading on the purple. What the voltage is will depend on how much fuel is in the tank.

You will only have power to the gray for 2 seconds after the key is turned on to prime the fuel system. Then it shuts off until cranking begins. If you dont get the 2 second charge or constant 12v during cranking I would check the fuel pump relay. Location is in diagram below.

Rich
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Sep 20, 2019 at 12:43 PM
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