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Thread: TBI transplant, wiring question

  1. #1
    Carb and Points!
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    TBI transplant, wiring question

    Hello to all, first time poster here.

    I am currently in the process of transplanting a tbi 350 from a 1990 cadillac brougham into a 1981 bonneville. I have all the wiring torn out from the cadillac including from the motor to dash. I have neatly ziptied all the wires that run from the engine bay to firewall plug to easily sort them.

    The wiring diagram I am attempting to follow is from http://www.chevythunder.com/1228746_ecm_198992_tbi.htm

    I'm trying to keep as much as needed on my harness including the emissions plugs, while also getting rid of the excess.

    I have all the wiring from the interior still in a whole chunk on the floor and was curious as to whether I should try to save the firewall to interior plug or maybe if I should just cut the wiring for the 2 plugs that go directly to my computer than solder accordingly?

    I was originally thinking saving the firewall plug was the definite way to go but now that I'm looking at the wires lay here I feel like that may be way more work than necessary.

    Any opinions or tips are fully welcomed here! This is my first time attempting to go this far into a cars wiring, so please bare with me and some of my silly questions. Thanks for reading

  2. #2
    Carb and Points!
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    I guess basiclly what i'm asking is, the only wires I should need to save are the ones that plug into the computer and the obd port wires correct?

  3. #3
    Fuel Injected!
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    I'm not sure which firewall plug you are referring to, the ones behind the fuse block that disconnect and the power and signals and such pass through or the one that the TBI computer wires pass through?

    The TBI wires should go through a thing that seals the hole in the firewall but can't be disconnected. You should find most of the computer wires go direct from the engine to the computer but that there will be some that branch out to the under dash wiring. The direct wires should be able to be kept. The wires that tie into the rest of the under dash harness can be cut wherever you decide is suitable. You have to tie them into your car's under dash wiring. You'll probably just extract the OBD port and enough of a wire tail you can make it work in your car.

    In the past, I have cut-out the firewall hole filling plug out of the harness so I didn't have to deal with it.

  4. #4
    Carb and Points!
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    Thanks for the reply I really appreciate it. So the firewall to interior connector i was referring to was just a bulkhead connector that runs the ecm wires into the interior along with some extras that I have worked out. I was considering removing the bulkhead connector and soldering all the wires together but figured that would be to much busy work to clear up a small amount of space. I think it's safe to ignore my first 2 posts but now I have a slew of new questions if anybody can give input on any of them that would be awesome.

    1. Gray W/red wire, under the hood it runs to a relay. The relay has 2 unknown plugs with 2 wires on each, I do believe each plug runs to a ground on 1 pin, and the other wire running to the 2 unknown plugs I believe is a blue wire? Relay also has 2 brown W/white wires coming out of seperate pins on the relay , than splice together leading to what I believe to be the alternator plug. -On the intererior side of the Gray W/red wire it is disconnected and at this time i'm currently unsure what it is supposed to lead to.


    2. Pink W/black wire, connected to emissions plugs. There is 4 emissions related plugs that tie together, than I think it also used to tie into fuse box? or maybe the oil pressures switches pink w/black wire? Emissions isn't necessarily my biggest worry at the moment but still would like to know for the future.


    3. Gray wire, ECM B2 Fuel pump input.
    -engine side of this wire has a single plug test connector? or maybe it plugs into something else? Also has a split leading to what I'm pretty sure is my oil pressure switch.
    -oil pressure switch has 2 other wires. 1st is Tan i'm unsure what that goes to currently, maybe oil pressure gauge or dash light warning? 2nd is Pink W/black I was thinking this might tie into the emissions pink w/black or go to a fuse??


    4. Fuel injector power wires- do I just fuse these wires to a constant power? Should it just be key on power? I think the ecm grounds the injectors to make them work so does it matter?


    5.ECM C9, Purple W/white, this wire I think goes to the small post on the starter? for some reason I have a fuse taped to the wire. Should it be fused?


    6. ECM A10, Brown VSS, comes from ECM goes to a plug. I'm guessing that plug went to 1 of 2 sensors used to determine the vehicles speed. The plug still has a power and ground tied to rest of system but also has 3 unplugged mystery wires. What would be the correct way to hook up the vss during the swap if the car receiving the system doesn't already have vss in place?


    7. ECM A8 Orange wire, diag enable In. Comes from ECM goes to ALDL connector, also has a tie point that splits off to the unkown. Anybody know where else this should go? Is it possible to leave unplugged?


    8. ECM A6 Pink W/black, Power In. This ties to a handful of points, I have a 7.5amp fuse taped to it, should this be on a key on power source?


    9. ECM B1 and C16 Orange, 12v battery In, I have 3 amp fuse taped to it, Should this be constant or key on power?


    10. ALDL connector, Pins, H- Tan W/white, J-Green, M- Tan, are all unplugged. I think the green wire might go to the same plug that ties into the ecm's vss wire? I'm guessing these wires can be left unplugged can anyone confirm?


    11. The main starter lug and distributor get power straight from the battery correct?


    For anybody who has bothered to browse through or read this in detail I thank you very much!!! Sorry to say this but once I figure out this set of questions I'm sure i'll come across a few more.

  5. #5
    Fuel Injected!
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    Here's a better source of info if you haven't found it yet.

    http://www.gearhead-efi.com/Fuel-Inj...Information-61


    I try to cover some of the wires.

    1. no idea. Might be car wiring not related to the EFI system.

    2. pink/black on emission solenoid plugs should go to switched ignition assuming you keep the emissions functions. The 81 probably has a charcoal canister so at least keeping the canister purge would be a good idea.

    3. B2 should be Tan/white and it goes to the fuel pump power. The single connector is a test plug to apply power to run the fuel pump. The oil pressure switch wiring can be completely eliminated. The other wires will be for a gauge on the car the engine came from so eliminate the plug and use the same oil warning or gauge sensor and wiring that 81 currently has.
    On the relay plug:
    E -> fused power
    C -> A1
    B -> black/white ECM grounds
    A -> B2 and the fuel pump

    4. Wire to ignition switched power. I think 5A fuse for each wire or 10A fuse for both would work.

    5. Yes, S terminal on starter. There was a fuse on that wire.

    6. A10 has to go to a VSS buffer. I'm not sure how it worked on that donor car. Some early stuff has the buffer in the cluster then switched to using a DRAC module for a while. So, look up DRAC module and see if the mystery plug matches. Either way, the DRAC module is the easiest way to convert the sensor for the ECM.

    7. The ALDL port serial bus wire goes to any computer modules in the car so it likely went to some other module. For the swap harness run it direct from the ECM to the ALDL port.

    8. A6 is the ignition switched power for the ECM. A 7.5A fuse would likely work fine for it.

    9. They go to constant power.

    10. Yes, they'd be fine unconnected. One would be power for a scanner though. Look up ALDL port wiring and you'll likely find better info.

    11. I'm not sure what exactly you are referring to, but the coil gets power from switched ignition. The distributor itself has no power wire going to it.
    Last edited by lionelhutz; 10-15-2016 at 05:25 PM.

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