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  1. #1
    Junior Member
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    Nov 2017

    Default JDM bigport wiring diagram

    I've recently purchased a JDM 4age out of a jdm halfcut.

    I've realised now that the wiring diagram will be different from the adm/usdm/eudm and the only one I can find is all in Japanese, would anyone have one laying around with English translations.

    It's a 3 rib TVIS JDM 4age bigport (blue top I believe).

    Would it perhaps be simpler to just install carbs instead? (if this is the case how much of the wiring do I need to get rid of? I havent look a lot into carbs and if anyone has very simple explanation when it comes to wiring for it that would be swell)

    Also the engine has the power steering pump and belt and the engine is going into a adm 4ac ae86 which doesnt have power steering (so ill delete it from the engine) and I cannot find the right belt online for the engine without power steering, what are my options? Would removing the power steering effect the wiring at all??
    Thanks any reply will be appreciated
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  2. #2
    Veteran LittleRedSpirit's Avatar
    Join Date
    Dec 2008


    Power steering can be deleted by removing the pump, reservoir, and lines. I dont believe there is any wiring that will affect running of the car.

    Carbys are their own source of problems, just different problems to efi problems. I would try to do the wiring and keep it efi for reliability, unless you want to wildly modify it in future, in which case an aftermarket standalone ecu would be best, but more costly and much harder to install than a stock ecu, as you dont just have to wire it, but tune it also.

    Theres a few kinds of carbys people use, webers, dellortos, fcrs. You can buy manifolds for each online if you search for bigport carb manifold, but then you need some carbs, and they really should be tuned by someone who knows their stuff. Personally I think the wiring of efi is more fun than the jetting of carbs.

    Plenty of folks on here are pretty experienced with wiring up a bigport, so just ask the right questions and you will get good answers.

  3. #3
    Senior Member Hen may possibly be a nut's Avatar
    Join Date
    Jan 2009
    Mt Macedon


    Any wiring diagram for a 4AGE AE86 should be fine. They are also at the back of the big green book (Toyota body manual). With this info you should be able to wire it fine. While it is personal preference, I would just wire the engine you have rather than change to carbs to avoid it. They bring their own problems and challenges.

    A very rough idea of wiring:
    - The wires in the big plug clipped to the middle of the firewall will need to be disconnected from the 4AC and reconnected to the 4AGE. These are starter signal, oil pressure for gauge, water temp for gauge, etc.
    - Alternator wiring will need to be changed to remove the external regulator and use the internal regulator on the 4AGE (it's like 3 wires).
    - Connect various wires to the ECU, mainly constant power, switched power, earth and just a couple from the rest of the car.
    - Fit and wire an EFI fuel pump. Control it with a circuit opening relay or similar.

    Then enjoy your newly 4AGEd car. It might seem hard initially, but a few hours working through the car and motor wiring diagrams will make it much easier.

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