Major Wiring Issue 84 Sierra 2500

Discussion in 'Classic GM' started by IsThrowingTools, Oct 4, 2016.

  1. IsThrowingTools

    IsThrowingTools New Member

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    General rundown: Bought a mostly stock 84 Sierra 2500 GAS, it's had a 350 crate motor dropped in. The wiring harness on the front end has been completely half assed, too many fuses connecting short wires, and grounds where they shouldn't be. It's a MESS. When I hit the ignition, it will crank, run for 10 seconds max, blow a fuse and die. As far as I can tell, this particular fuse is Only to feed power from the Ignition to the Starter. But it kills the truck when the fuse pops...
    I can barely make heads or tails of the harness in it's current state, so I'm hoping to start from scratch from the firewall Forward (under the hood Only, dash wiring is fine) I need a clear picture of a Correctly wired harness or the Original wiring diagram to fix this crap...help...
     
  2. JC00GMT800

    JC00GMT800 New Member

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    Google searches will definitely help with your wiring diagrams.

    Sent from my SAMSUNG-SM-G900A using Tapatalk
     
  3. IsThrowingTools

    IsThrowingTools New Member

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    Tried Google already for well over an hour, it won't pull up the correct harness for the Gas 2500, only the Diesel. If there weren't so many differences I would try to use that for a basis to go off of, but the harnesses are completely different. Also tried looking under a couple other similar vehicles and same problem, there's just too many differences that I know aren't supposed to go on this truck. Ended up running a hot wire straight through the system to get it running for now, but I'd really like to redo the Whole front end harness so I can avoid future issues with it. Haven't found anywhere that will sell it as a whole like they do on four wheelers either. If anybody could just post a picture of the Correct harness layout that would be absolutely fantastic
     
  4. daved931

    daved931 I have t-rex arms

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    If you buy a Haynes or a Chiltons manual, it should come with some wiring diagrams.
     
  5. kids-at-711

    kids-at-711 Sexually identifies as a shopping cart.

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    IIRC Painless makes a complete replacement harness for that truck. Its a bit pricey tho.
     
  6. daved931

    daved931 I have t-rex arms

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    At my last job we had a 1989 V30 and I bought the painless harness for it. I think it was $700.
     
  7. Kidd5298

    Kidd5298 New Member

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    Get the VIN number and take it to your local auto parts house an the should be able to pull it up an print out the whole wiring diagram. At least mine has done it for me twice. Can't stand the small print out in the books, no offense they're good but at 51 yrs old it's kinda hard to read. Lol
     
  8. Phildirt

    Phildirt n. fil-dert.

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    :hidesbehindsofa:
     
  9. ron7000

    ron7000 GMFS Member

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    let me know the specifics on the 350 crate motor, specifically
    - fuel pump, mechanical or electronic?
    - carburetor, or does it have any kind of fuel injection?
    - ignition system, distributor and if so is it electronic or does it have points?
    - what alternator are you running, and other than the main feed wire that is like 10 gauge in size coming off of it, how many wires are in the plug that plugs into it 1 or 3?

    being 1984 I am assuming it has a carb and nothing OBD related,
    if so wiring can be quite simple and i can send you a diagram as a starting point.
     
  10. tinfoil_hat

    tinfoil_hat New Member

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    All those fuses and grounds make it Sound like the PO had a short he couldn't track down. Is this starter fuse blowing at the fuse block or is it blowing at some inline fuse the PO added? What do you think about pulling a harness at the junkyard? Beats paying $700 for the aftermarket one.
     
  11. BoltspeedMen

    BoltspeedMen GMFS Member

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    Try diagrams for a 1500 v8. I had the same problem when doing a 94 a while back. Truck was actually made in December of 93, and still had the older 93 wiring. Ended up being all speakers wires he spliced into inside the truck.

    Regardless it's a carbed motor. And colt meter and two hours of your time will find the issues.
     

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