Author Topic: Wiring color for fuel pump question?  (Read 817 times)

Roadstir

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Wiring color for fuel pump question?
« on: October 05, 2024, 02:09:44 »


Just rebuilt my fuel pump, filled the tank with 5 gallons of non-ethanol gas, and used the pump's bleed screw to purge the air in the pump.  However, no joy.  It just cranks and cranks.  The pump worked fine on the bench, but once in the car I did not notice that old familiar whine when I turned the key.  So I am checking the wiring at the pump.

I'm slightly color blind and would like to know what color wire goes to which terminal on the pump?  Currently I have the black wire going to the positive terminal and the "not black" wire going to the negative pump terminal.  The "not black" wire looks a bit red to me.

Thanks~

Pawel66

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Re: Wiring color for fuel pump question?
« Reply #1 on: October 05, 2024, 06:24:46 »
In Mercedes world brown is almost always ground. There is a brown wire that may look like black that goes to "-". The positive feed is three colours.
Pawel

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BobH

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Re: Wiring color for fuel pump question?
« Reply #2 on: October 05, 2024, 09:21:56 »
Hello, your connections are the wrong way around, but even so i understood that these pumps would still run in reverse.  Perhaps you've popped fuse 4, or it's loose in the holder, or you have a bad earth/ground connection
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Pinder

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Re: Wiring color for fuel pump question?
« Reply #3 on: October 05, 2024, 16:14:22 »
if you rebuilt it with the housing in the wrong positon ,which has the magnets in it I think it will spin in the wrong direction. you can switch the wires around and it should correct the direction.
1970 280 SL Light Ivory DB 670. 4 Speed manual shift no AC Limited Slip Diff.
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Pinder

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Re: Wiring color for fuel pump question?
« Reply #4 on: October 05, 2024, 16:16:10 »
also if its not spinning it could be impeler is binding inside.
1970 280 SL Light Ivory DB 670. 4 Speed manual shift no AC Limited Slip Diff.
1997 Corvette C5 Silver. automatic
2015 BMW 320i xdrive
2021 Mercedes GLS450 Silver

rwmastel

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Re: Wiring color for fuel pump question?
« Reply #5 on: October 06, 2024, 21:39:52 »
Good advice to check fuse.  Disconnect the wires from the pump, have a helper turn the ignition on, and use a multimeter to determine positive wire.  It will spin backwards if wired backwards.  Might have to bench test again if it won't spin in either direction.  It's probably easy to put the impeller on upside down, which is bad.
Rodd

Did you search the forum before asking?
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BaronYoungman

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Re: Wiring color for fuel pump question?
« Reply #6 on: October 10, 2024, 03:52:27 »
Just a fyi ..yes the pump will still work and pump dome gas if it is wired backwards but will NOT ACHIEVE THE CORRECT PRESSURE AND FLOW.
Bob "Baron" Youngman
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