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Fuel Pump Replacement


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Before I pull my existing sending unit, I am trying to troubleshoot other possibilities to make sure the pump is getting power since my assumption that it is dead is because the truck died while driving it and I don't hear the pump coming on. I back probed from the harness side of the fuel pump and am getting 4v with the key on or when trying to start. Should I be getting more voltage??

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6 minutes ago, Ωhm said:

Your dropping voltage somewhere. Bypass (jumper) fuel pump ballast resistor. Take voltage reading at fuel pump harness connector again. Swap relays around. Take voltage reading at fuel pump harness connector again.

 

How do I bypass the ballast resistor? Jumper between the two wire clips? Which relay is for the fuel pump? I pulled those earlier and they appeared ok, i.e. no corrosion, and I sprayed them with contact cleaner. 

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5 minutes ago, Ωhm said:

That it.

 

 

Relay Block Pin_4 has ORN (orange) wire.

1358193878_RelayBlock.jpg.20ffbebe4b57089f7a488abb247260f9.jpg

 

 

Looking down at it from over the pass fender, which of the 4 relays should it be? Having a hard time getting the relay "tray" unclipped from the holder and don't want to break the tabs. Fyi, I am charging the battery with another car right now, voltage is 7.3v at the harness with or w/out the ballast bypassed. 

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3 minutes ago, WahooSteeler said:

Having a hard time getting the relay "tray" unclipped from the holder and don't want to break the tabs.

Yea, take your time there. Don't want to break any tabs.

 

4 minutes ago, WahooSteeler said:

Looking down at it from over the pass fender, which of the 4 relays should it be?

Fuel pump relay will have that ORN wire in Pin_4 of the 4 relay blocks.

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Ok. Couple of questions before I proceed.......

 

How much voltage is needed to the pump? Even at only 4v wouldn't the pump come on? 

 

I have some brand new relays that are 30/40 amp I was going to use for the door locks. What amp relays are in the relay tray, i.e. can I just try the new relays? 

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2 minutes ago, WahooSteeler said:

I have some brand new relays that are 30/40 amp I was going to use for the door locks. What amp relays are in the relay tray, i.e. can I just try the new relays?

I only meant to swap your current relays around. If fuel pump relay was a problem then swap in a different one.

 

4 minutes ago, WahooSteeler said:

How much voltage is needed to the pump? Even at only 4v wouldn't the pump come on?

Electric dc motors that don't spin are a direct short to ground. That why I asked to disconnect the fuel pump connector. No current flow in circuit. Now we're looking for battery voltage along the fuel pump circuit.

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2 minutes ago, WahooSteeler said:

Should the positive wire go to the purple, the orange/black, or both?

Purple wire is fuel pump sending unit (IP gauge). Orange/black is fuel pump motor.

 

3 minutes ago, WahooSteeler said:

And should the negative wire go to the black ground wire in the harness?

Yes

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