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4.0L J10 Swap Wiring Issue

Discussion in 'Electrical' started by designdca, Aug 16, 2019.

  1. Aug 16, 2019 at 12:22 PM
    #1
    designdca

    designdca [OP] New Member

    Joined:
    Aug 16, 2019
    Member:
    #3695
    Messages:
    1
    Gender:
    Male
    Vehicle:
    1977 Jeep J10
    New member, first post. I should probably start by explaining I've never actually worked on a vehicle of my own unless it had a carburetor - so no good experience with electronics. I recently bought a '77 J10 that a previous owner had swapped in a '93 4.0L drivetrain and electronics. Here's what was explained to me by the previous owner as best I can recall from the conversation a few weeks ago:
    It was all running fine and then one day he went to start it and....nothing. Like a dead battery, but battery was fine. He search and found a bad relay(?) near the firewall on the driver's side. He removed the relay and ran a jumper wire (photo attached). After doing this it started and was sitting idling fine when he noticed he had used too small of a jumper wire and it was overheating and melting the insulation. He turned it off and ran a larger wire - same configuration. After running the new wire, the engine turns over, but never fires.
    From what I've been able to investigate, I don't think the fuel pump is getting power. Other than this rigged up alligator clip situation that he did as a temporary fix, all other wiring seems pretty good and intact. Does anyone have any good, hopefully easy to understand suggestions of what I should check?
    Thanks!
    David

    jeep wiring.jpg
     
  2. Aug 16, 2019 at 4:13 PM
    #2
    Jim Beam

    Jim Beam Well-Known Member

    Joined:
    Feb 11, 2019
    Member:
    #2891
    Messages:
    596
    Gender:
    Male
    First Name:
    Donald
    Vehicle:
    1986 CJ7
    Fuel Injection, Dana 44s, T18, 4.10s w/lockers
    You should get some help by getting wiring diagrams for both vehicles, look up Prospero's Garage for that. When you first turn the ignition key to the on position, the fuel pump will charge up the system for about 2-3 seconds. Hook up a voltmeter to verify that.
     
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