Results 1 to 4 of 4
  1. #1

    Default HEI CFI computer question

    Hello all. I am new to the mid 80's Mustang world. I picked up an 85 LX 5.0 CFI auto, and am trying to get it running. It's been sitting for about 10 years. I wanted to get it running even if for 30 seconds before I pull it out to rebuild. It cranks but no spark. Also, the CFI butterfly is frozen solid. My plan is to throw on a 2 bbl carb I have laying around. Run an elec fuel pump to it (temporary) and throw in an HEI one wire dizzy (cast gear as I understand the CFI autos were flat tappet, not roller). My question is, it should start correct?? Would the computer keep it from starting for some reason?


  2. #2


    If you remove fuel and spark from the computer’s duties it won’t have much choice but to start — if this motor can run.

    I would avoid hacking into any of the car’s wiring, etc, but there’s no reason you couldn’t run a hot lead from the battery to the HEI then short the starter relay to force it to crank.

    Shutting it off would come via removing the power lead going to the HEI.

    When building the car you will want to research your options for induction and spark. Several CFI’s have been converted to multiport EFI and some to a carburetor.

    A lot of people cuss the ignition systems on the Fox. Personally I used the best thermal paste I could find when I swapped modules and haven’t had problems in over 20 years and several hundred-thousand miles.

    Some have moved their module in the name of less heat.

    One little known bit of info - the 90’s F250’s have an ignition module cooler and run the module over by the fender from the factory. It’s a design revision to help reduce heat and the resulting module failures.

    With either type of change no reason to avoid the duraspark - it will make more torque and run better with that system than it will with an HEI.

  3. #3


    Something for you to sink your teeth into... check out my Build Thread in red in my signature below, starting at about post #63, for THEE low-buck CFI to carburetor conversion process that has been completely dead nuts reliable for 2+ years now and I couldn't be happier with how well it runs even with a tired engine that I am replacing VERY shortly...
    1986 Mustang convertible ---> BUILD THREAD
    Past Fox-chassis "four eyes":
    1983 Mercury Cougar LS
    1986 Ford Thunderbird ELAN
    1980 Capri RS Turbo

    Work in progress website --->

  4. #4

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts