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modular mark 8 fox swap best/cheap/easiest way to wire engine

nathan

Active Member
hello and thank you for your time ahead of time. I am finally going to put this 96-97 mark 8 dohc engine in my 89 fox. I am currently looking through the forums so please excuse me if this exact question has been answered. I am completely lost on how to wire this engine into my fox. There is nothing left of the fox harness so wiring the modular harness into the fox harness is out of the question. When I pulled the mod engine I got every bit of the harness I could as I just had surgery on my shoulder and the pain pills weren't strong enough to permit me to continue. So with all that said, what is the easiest and most inexpensive way to get the fuel injection and ignition working on the car. I was looking into megasquirt and the detail zone wiring harness but I have the factory harness and really want to save some money. Thank you for your time.

Nathan
 

nathan

Active Member
it looks like the computer wiring harness is 12a581 so what im thinking about doing is connecting that harness to the engine but it looks like that then plugs into the chassis harness hmmm. righhhhhhht.....
 

FuturaGuy

Well-Known Member
Staff member
You came to the right place.

Under the Electrical Wiring heading, I have two stickies titled "Mod Motor Wiring in General" and "Wiring Harness". Under the Modular Conversion Discussion heading, about two-thirds of the way down the page, there's a post titled "My First 4.6 Fox Swap, any pointers?" Among the three threads there is a lot of good information on wiring.

If the Fox wiring is gone, at least under the hood, how about using the entire Mark 8 underhood wiring? It has everything you need both to run the engine and the rest of the car - lights, horns, A/C, starter, charging system, cruise control, etc. That's what I did, putting a 4.6 Cobra into a '79 Futura. The original '79 wiring under the hood wasn't compatible with the '88 dashboard or the Mod Motor, so I stripped everything forward of the firewall and used Modular wiring under the hood. Then I had to make a harness to connect the '88 dash to the Modular wiring. It really wasn't that difficult, just tedious, but it turned out to be very reliable and easy to fix when there have been minor problems. You'll need the wiring diagrams for both the Fox and the Mark 8 and a lot of patience.
 

nathan

Active Member
Ok thank you very much. I am going to look through them now. I spent some time with the eec harness and the other large harness that has the under hood fuse box. I found my ford 1995 mark 8 electrical trouble shooting manual . There are alot of wires on the car. I am currently trying to figure out what are the wired connections required to run the engine. And the other thing the manual was saying that car had a pcm and an ecu I only have the ecu so I'm not sure if I hafto have the pcm to run just the engine.
 

nathan

Active Member
So I read through your post on mod motor wiring in general it is good. I do have a question if I follow that should the engine crank and run . It's a 95 I'm a bit worried about the anti theft and the automatic transmission switch.
 

cpearson1342

Well-Known Member
If your car has pats or any other kind of immobilizer then you will need to disable it with a tuner for it to work. If you don't have a chip in your key then you're golden. All the wiring should be is connecting a few power wires to ignition that go to the computer for the most part. If you have the transmission in then you shouldn't have any problems with anything in the trans
 

nathan

Active Member
If your car has pats or any other kind of immobilizer then you will need to disable it with a tuner for it to work. If you don't have a chip in your key then you're golden. All the wiring should be is connecting a few power wires to ignition that go to the computer for the most part. If you have the transmission in then you shouldn't have any problems with anything in the trans
 

nathan

Active Member
Cool thank you. Yeah the 95 wiring manual says it had anti theft but from what I understand it is not the pats. I am going to by using a t45 manual until I blow it up it had an automatic so maybe I will just find that automatic trans sensor and complete the loop and see if that does it. And I guess all the harness needs to run is 12v to the starter solinoid and 12v to the computer, but I guess I will see in time.
 

cpearson1342

Well-Known Member
It's usually not just 12v to the computer, there's usually a constant power, and an ignition controlled one that turns on. I'll see if I can find some pinouts for you, or something useful.
 
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