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Conversion TBI wiring harness...

Discussion in 'The Garage' started by BlackDog714, Jun 14, 2004.

  1. BlackDog714

    BlackDog714 1/2 ton status

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    OK, so I have the TBI motor dropped in and now I am trying to wire it up. I have the TBI computer and harness. Can I strip everything out of the harness except the TBI computer controlled stuff? The harness I have is ONLY in the engine compartment. I know I can remove the headlight stuff, but I can also remove the charging stuff right? Where does the computer draw its power from?

    Thanks
     
  2. HarryH3

    HarryH3 1 ton status Author

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    The TBI harness is pretty much standalone. There is no headlight wiring in it. The headlight wiring is in the harness that runs down the drivers side fender.

    Off the top of my head... The computer needs:

    A constant 12 volts to keep the computer from losing its dynamic memory each time the truck is turned off.
    A switched 12 volts to "wake up" the computer when you start the truck.
    Connect the existing power feed for the distribtor to the TBI distributor. (If your truck had points before, you'll need to get rid of the resistor wire in the circuit).
    A switched, fused 12 volt feed to power the EGR solenoid circuit.

    A wiring diagram will make your task much easier. /forums/images/graemlins/cool.gif
     
  3. BlackDog714

    BlackDog714 1/2 ton status

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    The harness I got was the complete underhood harness that includes the TBI and everything else under the hood... Its all built into the harness.

    I have received a couple of wiring diagrams, but they just confuse my issue. I just need to know what I need to plug in and what I can get rid of.
     
  4. HarryH3

    HarryH3 1 ton status Author

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    What did the harness come from? I've never seen a factory TBI truck harness that included wires for the headlights and such. /forums/images/graemlins/eek.gif
     
  5. BlackDog714

    BlackDog714 1/2 ton status

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    [ QUOTE ]
    What did the harness come from? I've never seen a factory TBI truck harness that included wires for the headlights and such. /forums/images/graemlins/eek.gif

    [/ QUOTE ]

    Its from a 92 K2500 L05 with a 5 speed... the computer ends in 299. And the harness I have is every wire under the hood. Everything that plugs into the fuse panel.
     
  6. HarryH3

    HarryH3 1 ton status Author

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    All you need is the harness that goes to the computer. The one wire that provides power to the EGR solenoid may go off into another harness, over to the fuse panel, but the rest should be self-contained. The factory manual is invaluable for figuring out what goes where.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Be careful trimming ANYTHING out.

    As was mentioned, a manual will save your bacon here. If you cut something (like the charging circuit) out and find that somewhere down the line there is a splice that feeds something off of the TBI, you will be kicking yourself. Really have to read the manual, and make 100% sure there is nothing else relying on what you are cutting. A good way to do this is to cut NOTHING. Strip all the wiring out you THINK is extraneous, and if you can pull it from the harness without cutting, it is. If it's spliced, you better be darn sure you know to what, before cutting.

    You can fix wiring mistakes, but it's a lot easier not to make them in the first place.
     

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