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Thread: prepping for a swap

  1. #31
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    Still at the pink wires... can i just cut the pink wire that supplies power to the e-trans? Not running an e-trans in the truck. Also have a pink wire with a white tracer from the fuse block, was loose in the wire loom, never connected to anything ever. Can i also just cut that? Thanks again

  2. #32
    Fuel Injected! bentrod's Avatar
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    not sure as I dont remember this wire. I converted my truck to manual but the harness i was using was auto. However both transes have a VSS, so the other wires goign to controll the trans ride in the same loom going to the VSS connector. I just tucked the length of wires going to the trans control connectors into the loom, then left the connectors poking out.

    They don't get in the way. They dont dangle or look shotty. They arent hurting anything, weigh 0.1lbs and would only end up in the trash if I cut them. Moreover, in the unlikely case I ever sell the truck or engine or harness, the connectors are there which I believe adds value (who wants to buy someone elses cut-up, undocumented project that has this or that connector missing?)

    Same was done for the A/C. Just labeled them, tucked them into the looms, and taped it up. Theres so many wires and looms on these EFI cars that it's not even noticeable
    Last edited by bentrod; 07-28-2013 at 12:13 AM.
    1990 GMC C1500, 5spd, 1993 LT1 (ECM 16159278 $DA3)

  3. #33
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    You have a good point. So far anything ive pulled has been wrapped and labelled. Im just trying to limit how much stuff is running around since the truck goes crashing through the woods and from time to time 4+ foot of swamp. Less stuff to snag or cram full of mud the better and should something ever go sideways id love to have less wires to sort through fo find the issue.

  4. #34
    Fuel Injected! bentrod's Avatar
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    I know what you're saying. Less is better for a lot of things, but more adds modularity. Also there's a point where making less is much more time consuming than making more (leaving it as is). Then you have the factor that maybe you wanted that wire after all and are now adding it back, taking more time.

    A friend put a 1990 TPI into an 1987 S10 not too long ago and he was going the same route, pulling his hair out fretting over a wire or 2. This was a year ago. I did my part setting up what I could. Still, the truck isn't "done" and every time i go over there, there's a bunch of wires spralled out under the hood (work that I already neatly done and taped up).
    1990 GMC C1500, 5spd, 1993 LT1 (ECM 16159278 $DA3)

  5. #35
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    Do my level best to explain what im working with here. These to plugs are on the harness going into the truck. The two wire red goes to a fuaible link the grey goes to the wiper motor plug. The big one has wires going to the pcm and a few others i can trace.

    These plugs are what are original to the truck. The 4 wire has the same red and the twisted v.s.s. wires and the blue wire for the v.s.s. buffer. The clear plug has wires going to the pcm but i cant trace the others. This harness was cut at the firewall, not my doing.

    Does anybody have a pinout for these plugs? Searching has only found me the wires going to the data link plug. Different color wires and plugs and id like to know whats where. Thanks again. Should add i need to go from the top plugs to the bottom...
    Last edited by conwaymuddy; 07-28-2013 at 06:57 AM.

  6. #36
    RIP EagleMark's Avatar
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    Pretty sure that big plug in first picture goes to the dashboard.

    The black plug with twisted pair went to DRAC/VSSB.

    The clear one gets connected to vehicle and seems I have a pile of them cut off.

    Let me give you another idea about how to go about this... your looking at the wrong end!!! Start at the PCM plugs and one wire by one wire find out what you need. Starting at plugs that came off vehicle from other end is not going to help and seems to have you stuck in your thinking process.

    You pull the EFI harness off a vehicle and most of it is for running the engine and trans... but there's also some vehicle wiring in there, like you found a wire to wiper motor or switch? Well I've never seen any wiper motors hooked to the PCM? Also there are altenator wires in the haness you probably can't use, AIR pump, EGR etc... then the plug into dashboard? Well if you don't have that dashboard to use it's all got to be rewired and that plug is use less. The reason it has some wires from dash baord plug to PCM is IIRC the VSS is in dashboard of that truck? If not then there is CEL which needs power and the wire to PCM is ground... all depends on vehicle you pulled it from. Then what it's engine managment Stand Alone purpose is.

    You'll find that most power comes into harness from fuses and relays and then used by PCM, the PCM is the ground like for injectors, power goes into injector and PCM grounds to fire injector. Only power coming from PCM is 5 volt, ususlly 12 volt is going to device, power is not coming from PCM.

    Rule of thumb for colors:
    Red and Orange is 12 volt power alwasy on.
    Pink or Pink/Black is key on power.

    Grounds can be Black, Tan and grey. Be careful with these as they have different purposes.

    Recap: Start at PCM plugs to whatever on engine.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  7. #37
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    I have figured out the wires going to the data link since they come from the pcm to the big black or clear plug. The stump of a harness is from a 93 gmc truck with 5.7 auto, new harness is from 94 gmc 5.7 auto. I know theres a bunch of junk i dont need but id like to keep things that i can use. Most of the wires on the new harness i can trace, its just trying to figure out the old stump. I figure if im reworking this mess i should use everything i can and get rid of all i dont want/need.

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