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  1. #1

    Default carb to efi conversion question

    I am in the process of converting my 85 to efi. I have the fuel tank, pump, and lines, upper and lower intakes with throttle body, all sensors, efi dizzy, fuel rail, regulator and injectors, mass air meter, and wiring harness from a mass air car. what else will I need wiring harness wise to make it all work? oh the pcm I will buy new.

  2. #2
    Moderator wraithracing's Avatar
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    You will need either the harness or the wiring for the fuel pump, fuel pump relay, inertia switch, sending unit, etc. in the back.

    When you say you have the wiring harness from a mass air car, what year model and what exactly do you have as there are a couple of harnesses that make up a complete system.
    ​Trey

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  3. #3
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    And i did not see the 02 sensor harness mentioned ,which is different between the manual and automatic trans .
    clowns to the left of me , Jokers to the right

  4. #4

  5. #5

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    Quote Originally Posted by wraithracing View Post
    You will need either the harness or the wiring for the fuel pump, fuel pump relay, inertia switch, sending unit, etc. in the back.

    When you say you have the wiring harness from a mass air car, what year model and what exactly do you have as there are a couple of harnesses that make up a complete system.
    is the harness for the inerta switch and all a contained harness? or does it run in with the rest of the electrical system? reason I ask id that I may be able to get that harness but if it kills his lights or other things he may not want to separate it

  6. #6

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    The inertia switch is in the rear harness with the taillights and the sending unit/fuel pump harness. You will have to find one on fleabay or MPS or a local yard. Good Luck with it and youre gonna love the EFI once you get everything sorted out.

    Mike
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  7. #7
    FEP Supporter Broncojunkie's Avatar
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    Let us know if you're able to find a new ecm. I know they're still listed at some parts stores, but they always seem to be out of stock. And also, have you considered going with a stand-alone system? After you buy all the required parts to use the factory stuff, you could probably be into one of the aftermarket kits, which are a lot easier to install and less problematic.

  8. #8

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    thanks for the help. I got a rear harness local. I already have everything else....2 sets.....I will let you know if I find a ecm local.

  9. #9

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    Honestly I would track down a complete harness from an 86 then do a MAF conversion on it. Then everything will look factory and just plug in and the car won't be a Frankenstein.

    Other builds documented here have done exactly that.

  10. #10
    FEP Power Member
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    What about the Holley bolt on EFI kits? Are they any good?

  11. #11

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    Quote Originally Posted by erratic50 View Post
    Honestly I would track down a complete harness from an 86 then do a MAF conversion on it. Then everything will look factory and just plug in and the car won't be a Frankenstein.

    Other builds documented here have done exactly that.
    What's wrong with a Frankenstein?
    Brad

    '79 Mercury Zephyr ES 5.0L GT40 EFI T-5 (Mustang LWB)
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  12. #12

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    Nothing if you don’t mind working on it when it decides to be Frank on you.

    The number of shops willing and able to work on foxes is dwindling. Personally I would use an 86 harness then do a MAF conversion because it makes it so very straightforward. Just my opinion for what it’s worth. It plus the price shown on the machine will buy you a coke....

  13. #13
    FEP Power Member Ourobos's Avatar
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    Done several.. Best way to save you headaches and pulling your hair - Find an 86 5.0 ECU harness, driver side engine bay harness and the tail light harness which contains the fuel pump circuit - all from the 86. Then convert it to mass air with the MAF plug and 4 wires or so.
    1986 CHP SSP Coupe

  14. #14

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    Quote Originally Posted by tiptopss View Post
    What about the Holley bolt on EFI kits? Are they any good?
    I/we just installed one of the Fitech efi systems on my '84 Capri RS.
    We had some teething pains during the initial install but now it seems to be working okay.

  15. #15

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    If I were doing one, a complete 86 harness is the likely direction Iíd go.

    It was the Ford engineerís answer, thatís perfectly clear when you really compare the 85 vs 86 cars.
    Last edited by erratic50; 05-27-2018 at 05:53 PM.

  16. #16

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    Why go easy? Take the best(?) Of both worlds and put a ford CFI on it! All the headaches of a computer and wiring harness plus a TBI system too!!!

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