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Thread: LS3 wiring help needed

  1. #1
    Registered Member
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    LS3 wiring help needed

    Howdy Folks,
    Need some help here. I have the LS3 crate motor with a 6spd. I'm trying to wire the in-tank fuel pump. The "instructions" say:
    "The fuel pump is controlled by the ECM. The control wire supplies12 V and is fused/relayed and should connect to the 12 V side of thefuel pump." My question is, does anyone know where this wire is to be found? None of the wire positions in the "instructions" are labeled fuel pump.
    Thanks in advance... I know you guys will know.

  2. #2
    Registered Member WagonCrazy's Avatar
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    So you want to know the fuel pump control wire coming out of your ECM.
    Are you using a stock ECM from a ? year/model chevrolet....

    You will need to look up the specific pinout location # for that ECM.

    it will become the trigger wire to Pin 86 on the relay.

    Fuel Pump Relay.jpg

    alot more info can be found on lt1swap.com
    1957 Nomad- LS1/T56 on C4 chassis
    1959 Fleetside Apache 1/2 ton, shortbed, big window, 327ci.

  3. #3
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    If you have the LS3 crate engine controller/wire harness, there is a fuel pump relay in the fuse and relay panel, its output is a gray wire marked "fuel pump" that comes out of that panel. Most production setups and aftermarket harnesses that use a GM controller will have a similar setup, though no guarantee the wire is gray.

  4. #4
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    I knew I could count on you guys.... You folks are the best. The diagram makes sense and I find this configuration in the crate motor fuse box.
    I do have the controller that came with the crate motor. Tomorrow I will be pulling the harness out of the loom to find that gray wire.. Thanks guys for the help.

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