Electrical Converting 83 Fox To Efi With Complete 88 Motor.. Questions

MI.4EYEFOX

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Hi there, new to the forum but not new to fox bodies. I do need some help though. I'm converting my 83 fox to EFI by installing a motor out of an 88. I have the complete motor, injector harness, PCM harness and O2 harness. The question that I have is there are a couple connectors on the engine harness that would plug into the 1988 mustang wiring that my car does not have, for instance there are two connectors a black and a gray that would reside behind the driver side strut tower and those connectors would plug into a harness that goes to the dashboard of the 88. There are a couple wires on that connector that I have been told are for engine crank and engine crank/run. what am I supposed to do with those? I'm assuming those would need to be connected to something on my cars ignition wiring?!

There is also a green six pin connector (only 4 pins inside) that is extremely close to the PCM connector that I have no idea what it is for.

Any help would be greatly appreciated. If you have done a swap like this before I would be greatly interested in any advice you could share. I'm sure it cannot be that difficult since I have all of the engine wiring as I have been told by some people it is as easy as supplying power and ground.
 

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MI.4EYEFOX

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Thanks for the info. I believe I have already seen some of the wiring diagrams that he has put together. I was hoping to find someone who has already done this swap and had a diagram of what goes were.
 

jrichker

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Your best bet is to do two things:
1.) Buy a Chilton manual for an 88 Mustang - it will have the wiring diagrams which have the connector shapes and wire colors.
2.) Post a detailed description of the connectors and the wire colors associated with them. Photographs of the wire colors are no good, because the color rendition from one computer to another is not the same. What looks hot pink on one computer looks like red on another computer.
 
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MI.4EYEFOX

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Maybe my first post was a little misleading. In one of the photos that I posted there are 2 connectors one black and one grey. The grey connector has 2 wires in it that are for engine crank and engine crank/run. My question is do I need to connect those to any of my original 83 wiring for the engine to run? If so what original 83 wiring would I tap into?
 

Mustang5L5

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It's tough to identify thpse plugs without reference as to where in the engine bay they would be located. I can think of several plugs that they look like, but without knowing what the location of the plug would be in, it's tough to say if it's needed or even what it went to.
 

Mustang5L5

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Here is the wiring for a 1988 drivers rear apron area
96917945fef4ffe47e7853772326b27b.jpg



What you are holding in your hand is C403 and C201, and you are right, they tie back into the dash harness that runs inside a 1988. Inside those plugs, are wires for the low oil relay, the neutral sense circuit, transmission wiring such as the VSS and other wires which aren't present on your early Fox mustang. You are going to need some of these to get the engine to run well.

I'm not familiar with EFI swaps, but I'd imagine you'd want to get two pigtails from a 87+ car that plug into these with 6" of wire, and a 1988 EVTM like I have here, and start tracing some wire colors out.


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Mustang5L5

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For example. Here is the wiring for the low oil relay which is located under dash on drivers side near clutch pedal on 1988

ef3d139ddf70e5be93f463c8b48a68cd.jpg


C166 is the connection of the o2 harness and c403 is where the white/pink wire goes inside to the relay. Unsure if the 83 has this relay, so you'll need a way to splice into it if present


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Mustang5L5

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Also one of the more important one. Pin 30 off the ecu goes inside the car at C201. It ties into the switches on the clutch pedal and t5, which may not even be present in an 83.

e4bf16eb314178cb31e8003a71fa3133.jpg



There are work arounds. I'd prob just ground pin 30.


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Mustang5L5

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As for the green connector? Which one does it look like based on proximity to ecu connector?
54ba87cf3e74512372db5ba46f222042.jpg



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MI.4EYEFOX

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The green connector looks to be C135

Reading electrical schematics is probably my weakest point. So I really appreciate the help.
 

Mustang5L5

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The green connector looks to be C135

Reading electrical schematics is probably my weakest point. So I really appreciate the help.

Quick check, power for the O2 sensors passes through this plug, as well as SigRTN from the clutch and trans neutral switch pass through here and return to the ECU. All critical.


Unfortunately, you are going ot have to dig into the wiring a bit more here. You might have to pick up a dash/trans harness from an '88 as well and do some splicing.
 

MI.4EYEFOX

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Oh that's just wonderful! The reason I decided to go this route was because I read somewhere that you pretty much just had to put a power and ground to the harness and you were good to go... ugh!
 

stykthyn

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Holy hell that price is insane. You're going to need an 87-88 dash harness. Not sure if an 86 would be compatible or not. If it is you could still probably keep the hook ups for your gauge cluster.
 

jrichker

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LMR has a harness that apparently is meant for doing EFI swaps. I wonder if I should just go that route?
That's a Mass Air harness that requires a different computer and a MAF, use a A9L, A9P and a MAF.

94-95 Mustang GT MAF - $40-$100. It is 70 MM instead of the stock 55 MM on regular stangs built prior to 94. This is a direct one for one swap that does not require any tuning or programming, It uses a slip on duct on the side that goes to the throttle body and a 4 bolt flange on the other. You need a flange adapter to fit the stock slip on air ducting that goes to the air box. Wiring plugs right in with no changes. *1 *2

*1.) Metal flange adapter http://www.kustomz.com/components.html Buy the TR70 for $40. Or spend some time on eBay looking for one that may fit.

*2.) MAF & sensor interchange
The 94-95 Mustang 5.0 MAF & sensor is also found on:
1995-94 Mustang 3.8L F2VF-12B579-A2A,
1994-92 Crown Victoria 4.6L F2VF-12B579-A2A,
1995-94 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
1994-92 Town Car 4.6L F2VF-12B579-A2A,
1994-92 Grand Marquis 4.6L F2VF-12B579-A2A,
Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.
 
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MI.4EYEFOX

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I'm picking up a factory programmed A9L this Saturday from a local guy who has one for sale.
 

Mustang5L5

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I don't know enough about 5.0 efi swaps to recommend one harness over the other. I just know that the 5.0 computer is looking for certain things, and if not present, can affect how the car runs.
 
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