4cyl and 8cyl harness questions

BK_CAULEY · Jan 11, 2008

i will try and make this as simple as possible. i am doing a 4cyl/ 8cyl swap and having some issues. the ECU side of the harness is a breeze. But afer the harness passes the 10 pin connectors and goes to the driver side it connects to the dash harness coming out of the firewall under the brake booster. i removed the harness form the v8 car (entire thing minus dash harnes) because i was under the impression that it connects back to the 4cyl dash harness, but this isnt happening.

everything on the ECU side matches up great but i have 2 connectors coming from the main v8 harness that do not match the up. can someone please tell me how this is supposed to work. or do i have to replace the entire dash harness too. if i do i am going to abandon this swap before i get any further.

this is the v8 harness's plugs im having difficulty finding a home for.

this is the 4cyl harness coming out of the firewall.

these are the only plugs that are even close to be the same size as the v8 cars.
but the are not the same. shaped a litte different and are different colors. the
ones on my v8 car are all black.

which ones are the ones i have circled in red in the first picture? hell do i even need to hook them up. im sure they are there for a reason but there isnt a spot for them on the 4cyl harness.

SVT32VDOHC · Jan 11, 2008

What is the years on both cars??? When I swapped my 92 5.0L stuff into my 91 4cyl car everything worked out perfect. I used the stock 4cyl dash harness, which ran through the drivers firewall to the selenoid. I hooked up all the 5.0L wires from ECM to engine. You also need to use the 5.0L headlight harness because the alternator plugs are incorporated and on opposite sides. IF your years are too far off, then you might have to use the 5.0L dash harness.

BK_CAULEY · Jan 11, 2008

i have a 3g alternator but i can use the 5.0 headlight harness if i have to.
my v8 car is a 1990 and my 4cyl is a 1991. please tell me i dont have to pull that dash harness and swap it too. how hard is that? it looks like alot of stuff.

BK_CAULEY · Jan 11, 2008

ok i found this brown connector that has the same connector style has one of the mysterious ones off the v8 harness. the brown one will plug up but it has a different number of wires and none of the wires colors match AT ALL. but there isnt anything else on the dash harness coming out of the fire wall.

i dotn know if the grey connector on the 1991 is supposed to be the same thing as the grey on the 1990's or not. if it is well good one down one to go. the black one not close to anything.

here is the brown wire but you can see its got the same housing but not the same plug pattern. i took the picture of the female ends of both plugs. the brown plug has 8 pins on the male side.

FOUND SOMETHING the brown eight pin connector is on the diagram above. its number 31. so im guessing the grey one on my 1990 does plug into the brown on the 1991. so where does the black go?

this si the grey ones on my v8 car

88mouse · Jan 12, 2008

From 87-89 Is A different harness from 91-93, and 90 is a year of its own. You will have to change the dash harness to.

strtrcr50 · Jan 12, 2008

Jhr351 has the harness you need in this thread and you have the harness he needs. Perhaps you can trade.

jrichker · Jan 12, 2008

When you post pictures of electrical wiring, always post the year model of your car along with the wire colors including the color stripe on the wires. The wiring color codes are a clue to the wire function. A list of the colors is helpful along with the pin to color assignment. The connector shells always have a letter or number on the shell for each pin.
Example:
connector pin A= blue/white
connector pin B = red/green

Ford changed the color for some wires in 91, so that's why the year model is important.

Also show an extra picture of the non wire side of the connector so that we can see the connector shape and how many pins are in the connector. That helps identify the circuit function since most of the connector shapes are unique to the circuit they serve.

BK_CAULEY · Jan 12, 2008

ok ay i will get some more pictures tommorrow. will swapping to a 1991 harness fix al my problems? or am i gonna have to still splice stuff?

88mouse · Jan 12, 2008

BK_CAULEY said:
ok ay i will get some more pictures tommorrow. will swapping to a 1991 harness fix al my problems? or am i gonna have to still splice stuff?

If you change the dash harness you will be good to go.

BK_CAULEY · Jan 13, 2008

88mouse said:
If you change the dash harness you will be good to go.

im trying with everything i have t o not have to swap the dash harness. i want to know if i get an engine harness from a 191 will that work? i want to leae both dash harnesses in place.

ok i have found something online for the black plug on my car. could anyone explain to me what these abvreviations meen. and do i even need the black connector. can i just plug the grey one form my 1990 v8 car into the borwn one on my 1991 4cyl car.

Mr. Rustypwnz · Jan 13, 2008

yes get the engine harness, and headlightharness from a 91-93 and thats about it, then, swapping the fuel lines are the harder part of it all..

88mouse · Jan 13, 2008

slow95gt said:
yes get the engine harness, and headlightharness from a 91-93 and thats about it, then, swapping the fuel lines are the harder part of it all..

I don't think that is going to work for him.

A 90 dash harness only has one plug in that hooks to the engine harness. It is the only year that is like that.

One way or another your going to have to change the dash harness.

jrichker · Jan 14, 2008

BK_CAULEY said:
im trying with everything i have t o not have to swap the dash harness. i want to know if i get an engine harness from a 191 will that work? i want to leae both dash harnesses in place.

ok i have found something online for the black plug on my car. could anyone explain to me what these abvreviations meen. and do i even need the black connector. can i just plug the grey one form my 1990 v8 car into the borwn one on my 1991 4cyl car.

I do not know if this matches the plug that is in your car. There are no wire color codes given to match what you have. However, it does describe the functions of the pins in the connector you showed.

HEGO = Heated Exhaust GAS Oxygen sensor
You have a LH sensor output and a RH sensor output
You have 12 volts to the sensor heaters
You have the power ground for the sensor heaters.

NDS = Neutral Drive Safety switch. This grounds pin 30 on the computer so that you don't get code 67 and can dump the engine running codes. It connects to the Neutral Safety Switch on the top front of a T5 On a Tremec 3550/TKO/TKO500/TKO600, the Neutral Safety Switch is back by the shifter handle mount.

Manual = use this pin for the 5 speed transmission.

Auto = use thes pin for an automatic transmission

Low oil sender - connects to the sender on the driver's side of the oil pan.

BK_CAULEY · Jan 14, 2008

thanks for the reply. i guess im going to just get a harness froma 1991. i spoke with svt32vdohc and he said he had to use a 1991-93 harness and it was all plug and play and he didnt have to swap the dash harness so im going to g owith that and try it. im going to keep the 1990 v8 car around just in case i end up having to swap everyhing.

2manypony's · Jan 14, 2008

Need to jump in on this one...

I just had a similar situation and just want to clarify before I go pulling the dash harness that I just started to install yesterday. I picked up a '93 LX 5.0 a couple weeks ago that had a small fire in the dash, due to someone's poor A-Pillar Gauge wiring job. I thought that '90 thru '93 dash wiring harnesses were the same, but when I ran it thru the firewall and compared it to what was left of the old harness in the engine comparment, I discovered otherwise. The '93 harness has the single round "brown" connector as you just come thru the firewall and the '90 dash harness that I picked up has the two round "grey and black" connectors. From what I read in this thread, '90 is different than '91 thru '93 and I need to start looking for another dash harness right away. Is this correct? Does anyone have one laying around they don't need and/or does anyone need one from a '90 5.0 GT by any chance? Thanks!

KGOFF · Jan 14, 2008

http://www.veryuseful.com/mustang/tech/engine/

BK_CAULEY · Jan 14, 2008

KGOFF said:
http://www.veryuseful.com/mustang/tech/engine/

yea. thats the first place i turned too. i have went over every diagram in there and they are all referencing the 1991+ harness. none of them show the 1991- harness.

TC93 · Jan 15, 2008

Here's what I have found out over time..

89 engine harness will work with 87,88 & 89 dash harnesses..They have the bl & grey plugs..

90 engine harness will only work 90 dash harness-- have the grey and blk plug like the 89's. And will plug into a 87,88 & 89 dash with no problem. But car won't start. Have heard it can work with some re-wiring, but never tried in personally. But know for sure a 90 won't work in an 87-89 car without swapping dah harness or getting 89 engine harness, learned that the hard way. To tell 90 harness from 89 is to look for white connectors by the MAF connector and where starter solenoid connections are. Those are for the air bag sensors.

91 hanress will go into 91-93's but not sure if it works in 92 & 93's cars.. The 91-93 engine harnesses look the same but the 92-93's have the fuel pump relay on it by the MAF connection, next to the AC WOT cut out relay, and the 91's doesn't. The 91's still use the fuelp pump relay under driver seat..

BK_CAULEY · Jan 15, 2008

and thats the kind of advice i was looking for. so i just need a 1991 dash harness and im good then. thanks man.

Myke86GT said:
Here's what I have found out over time..

89 engine harness will work with 87,88 & 89 dash harnesses..They have the bl & grey plugs..

90 engine harness will only work 90 dash harness-- have the grey and blk plug like the 89's. And will plug into a 87,88 & 89 dash with no problem. But car won't start. Have heard it can work with some re-wiring, but never tried in personally. But know for sure a 90 won't work in an 87-89 car without swapping dah harness or getting 89 engine harness, learned that the hard way. To tell 90 harness from 89 is to look for white connectors by the MAF connector and where starter solenoid connections are. Those are for the air bag sensors.

91 hanress will go into 91-93's but not sure if it works in 92 & 93's cars.. The 91-93 engine harnesses look the same but the 92-93's have the fuel pump relay on it by the MAF connection, next to the AC WOT cut out relay, and the 91's doesn't. The 91's still use the fuelp pump relay under driver seat..

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