Hooked up wiring harness and car wont start

[stevesLX]

O.K. guys I need some help!! I have a 89 LX and I hooked up a used wiring harness for the computer last night and upon completetion I tried to start the vehicle and all it did was crank it would not turn over. The harness I got was from a 1990 mustang. Everything was identical except there was a xtra plug down where the harness hooks up to the computer. My old harness didn't have that. There was a relay over by the Mass airflow plug. My old harness that was cut off. And over on the drivers side corner by the firewall where you would hook up to try to pull codes there was 2 plugs that plug into another harness one is black and the other grey. The black one went together fine but the gray one had like a lip on the inside of it and until I removed the lip I could not get it to hook up. I also noticed that my old one didn't have that lip inside of it and it had like 6 wires coming ou of it and the one I finally got hooked up only had 4 wires and there was a 5th one but it was cut. The only other goofy thing I noticed was the ground on the harness over where the silenoid is had a fuse holder on it. Black wire w/green stripe. Beyond that I dont know what could be wrong other than bad harness maybe. I thought maybe I hooked up my injectors wrong. I haven't tried flipping all the plugs over yet but I beleive they will only hook up one way. But like I said it just cranks and wont kick over or even try to kick over.

 

[jrichker]

The 90 harness is only compatible with a 90 model Mustang. It could be made to work, but you would have to have both sets of wiring diagrams side by side to compare and swap things around. That demands a high degree of electical expertise.

Copied From bbunt302

Just for reference, here's a list of all the compatible years:

89 harness should work for 86-89 as long as you're using mass air.
90 harness will only work in a 90. (B/c of air bags and dual dash connectors)
91 through early 92 harnesses should be compatible (single dash connector, fuel pump relay under driver's seat)
Late 92 through 93 harnesses should be compatible (single dash connector, fuel pump relay under the hood)

Computers from 89-92 are all the same. Look for the A9L sticker on the back cover for a 5 speed that matches your requirements. Example: E9ZF 12A650 AA" with the A9L code.