85 CFI to EFI swap guys.

[94opalgt]

What wiring harness did you use? I'm being told that the only way to do it is by using a harness out of an 86 GT and using some kind of piggy back harness for Mass Air.
Let me know, thanks.

[frankiesaysrelax]

Yup. 86 GT harness. No others will work without modification. I bought a wrecked '86 GT when I did my swap. Everything was plug 'n play. You can use an '87-'93 harness but you will have to do some splicing. For mass air you will need to add the wiring for the MAF. I did not do this as I stayed speed density.

[RFlora85]

Thats what I'm doing. I just bought an 86 GT harness, still collecting other parts for my swap. I'm going mass air though, still unsure on what to do to add that in the harnes yet though.

[94opalgt]

Ok then, I have a complete Mass air harness, what exactly do I have to modify on it to get it to work?

[Cobra Jet]

What type of MAF harness do you have - is it one from an 89-93 EFI Mustang, or is it a conversion harness from some aftermarket company?

As Frankie said - get yourself the 86 GT engine harness (dash & body harness to rear of car is not necessary) and of course the proper EEC. Swap out the original CFI engine harness and install the 86 GT EFI engine harness, hook everything up. If you did it correctly, the car should start right up (as speed density) and run perfectly fine.

To do the MAF conversion:
You will need the proper MAF (ie: MAF sensor matched to inj size).
MAF harness
MAF EEC (usually A9L, A9P, etc)

If you have an aftermarket EFI MAF conversion harness, most likely it should have come with instructions showing what PINs need to be swapped around in the EEC main harness. It's fairly simple to do.

If you are using the MAF harness from an 89-93 EFI Mustang wiring harness, you will have to read up on how to use it inconjunction with the 86 GT harness (if you intend to splice it in).

The EASIEST swap is to use one of the aftermarket MAF conversion harnesses, as it's usually a single harness and you just move some PINs around on the main EEC harness and you're done.

Remember, the 86 5.0 Mustang was the ONLY year EFI Mustang that had it's own specific wiring harness. After 86, the wiring harness was changed by Ford to incorporate the new aero body style (headlight harness, dash harness, etc). Today, it's very hard to source an 86 EFI harness - some get lucky, or some will buy a complete 86 5.0 and gut it for what they need.

Check with Frankie too - as IIRC, I thought the CFI fuel pump may need to be changed as well.... It's been quite some time since I mingled with the CFI to EFI swap. Frankie's 5.0 vert was the one he bought from me. When I sold it, I had already removed the autotragic trans and CFI engine and had started with the auto/CFI to 5spd/EFI swap. Frankie took it going forward and completed the conversion - he knows lots about the conversion details.

[86VertMK]

I used the now obsolete Ford Motorsports harness, which was essentially a stock 92-93 SEFI harness. I used the brute force method in unwinding the enitre harness that runs from the DS firewall, all the way around to the PS apron. I took the entire loom apart, and layed it out on the floor, ran the headlights, etc in a new loom, and then spent some time with the sticky wiring .pdfs here printed 11x17 (still pretty fuzzy) and also had an 86 and 93 EVTM on hand, and went about merging the existing V6 body harness to the 93 harness one wire at a time.

I also went to the salvage yard to get the correct connectors, and bought a ton of the ford crimp pins from motormite/dorman and a crimp tool.

It was a lot of work, and time consuming, but if you take your time, and double check as you go, it is not too bad. When you look at the finished product, you really cannot tell this was a transplant harnes since it all plugs together like factory.

I had a large dry-erase white board hung in my garage where I would sketch out what I needed to do using one color for existing and another color for changes required.

[lwelchx2]

So if i wanted to have a speed density EFI swap on my 85 cfi, do you need anything other than the 86 gt harness, intake manifolds, and tubing?