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Wiring help


Dude76

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I've searched over multiple sites, but the answer still seems to be eluding me. I'm in the middle of a EFI to carb swap on a 76 280z. I've removed the wiring harness and all that jazz, but now I need to power the fuel pump. I found a schematic on here that runs through the oil pressure switch, but it still isn't very clear.

I've located the connector to which the power for the fuel pump originally ran (under the driver's side dash) and removed the wires inside. Two of the wires run to the fuel pump and I assume the other two provide power. I want to use (hopefully) the original wiring with as little alteration as possible. I believe I can install a relay with the original four wires, but no matter how many diagrams I look at, I can't figure out which way it should be installed, or which side to install the fuse on. I want power running through the relay when the ignition is powered on (obviously to power the fuel pump), but not when off (duh!)

I have drawn up a diagram of what I am trying to connect. The relay is a SPST relay (a SPDT relay can be obtained if needed for this application).

The wires come from the following locations (in case it varies by year)

Grn/Blu - fuel pump

Blk/Whi - fuel pump

Whi/Red - Fusable link

Blk/Yel - Fuse panel

wiring.jpg

Could one of you electrical savvy types help me out? I would appreciate it greatly. Thanks in advance.

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The FSM does not indicate wire colors so I cannot help you there, but if you have a multimeter you can figure it out yourself.

Terminal 87 goes to the fuel pump.

Terminal 30 is where you put the fuse and 12V power you are going to use to power the fuel pump.

Terminal 85 is where to put the wire that has 12V only when the car is ON.

Terminal 86 is the ground wire.

(Terminal 85 & 86 are usually interchangeable unless there are polarity markings on the relay.)

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Thank you both for responding!Curtis that is what i needed to be sure thank you.sblake01 i am just using the stock wiring have replaced fuel pump with a low pressure electric pump.
Cool. That's why I posed it as a question as it hadn't been mentioned.
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Well I hooked everything up,nothing. No matter how I hooked it nothing. Icould connect pump to hot it would work,but i couldnt make the switch run it.Then i remembered the relay had to be grounded also,so i ran a ground to the switch wire(85)now it works like a charm.Now I have to run a wire to the oil sending unit to the relay so if i crash oil pressure drops and pump will shut off.

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Not yet.Giving my brain a rest.LOL!I know next to nothing about wiring,but this site has been great.Im just trying to bring a dead 78 280 back to life.If you have any Ideas throw em my way any help will be welcome. just talk as if your talking to an 8 yr old LOL.

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I could have been a lot more help to you if you had left the EFI system in the car. I've become fairly adept with the circuitry of that system. This probably doesn't apply much since you've removed the original wiring harness but only the 78-83 EFI systems use the oil pressure switch in the fuel pump circuit. The 75-77 used contacts in the AFM to actuate the fuel pump. You'll have to design your own circuit for that but it sounds like that is what you're doing.

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Yes I think Im on the right track.The EFI is pretty much a stand alone system.It only had 1 6 terminal plug(and only used 4 of them)connecting the system 2 the wiring harness.The more i work on it the more confident I get.I can pull motors trans wheel cyls you know turn a wrench with the best of them,electrical just mystifies me.As far as a oil sending fuel pump kill switch ive thought about taking the factory oil sending unit and putting in a T fitting and installing a gm style 2 prong sending unit just for the fuel pump.That way I still have factory unit for the gauge.

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