V8 conversion - 1988 Mustang

88turbo · 09-06-2004

I have an 88 Mustang Lx 4cyl I am converting to a 5.0. The 5L engine is out of a 93 LX. I have the complete donor car and everything i need for the conversion. My question is do I need to change the wiring harness goinginto the dash on the driverside of the car? Everything from the computer and out into the enginebay on the passengers has been swapped. As of now everything is connected using the 5L harness and the 4cyl dash harness is connected. The car turns over like it wants to start but doesn't start. Is the dash harness the problem? Any help I can get would be greatly appriciated.

GhostDog 5.0 · 09-06-2004

Can you hear the fuel pump come on? If you pull the #1 spark plug wire and put it close to metal are you getting spark ?

88turbo · 09-07-2004

No you can't hear the pump come. We wired the pump to a constant power source to make sure it was working. The pump works, its like its not getting the signal to turn when the ignition is turned on. We put gas in the throttlebody and it fired over for a second then died again. I hope i don't have to rewire the dash(PITA).

JUSTNLX · 09-07-2004

The 93 engine harness is not compatible with the 88 dash harness. The fuel pump relay is under the drivers seat on an 88 and in the engine compartment on a 93. Some connectors under the hood have also changed for the 92-93 engine harness.

You have a couple of routes you could go. Change the dash out and all the wires for the fuel pump or get the connectors off the 4 bangers harness and re-pin the 93 harness to 88 specs.

I my self would do the re-pin. I had to do this for my son's 90 conversion with an 88 (Calif) engine harness. I had to re-pin the 88 harness now it is up to 90 specs

88turbo · 09-09-2004

Thanks for the info. What exactly do i have to repin to make the 88 harness to work? Am i repinning the dash harness or bot the dash and computer harness? I just want make sure I have all the info I need before I start. I dont want render both harness useless.

JUSTNLX · 09-09-2004

The computor harness, or main engine harness,

The harness that goes to your headlights, signals and alt. will need to be repined too. Unless you keep the 4 bangers harness in and lengthen the alt wires.

Get a Helms factory Vacuum and wire trouble shooting guide for both the 88 and 93

http://www.helminc.com/helm/search_s...6PDGQ93RTU5ACF

Study it and make notes which wires would need to be switched. It will take some doing. Don't start moving wires until you completely understand where the wires will be moved to. Some wires will need to be moved from one side of the engine to the other.

One other option, can you trade or sell the 93 harness for a 88 Calif. or 89 harness? If you could, this would be the best thing to do.

88turbo · 09-10-2004

Thanx justnlx, an aquaintance of mine has an 89 v8 harness I can buy. I also have an 87 and an 88 harness I can use. Sounds like the 89 harness will be the best choice though.

BIG G · 03-14-2007

do you want to sell the 93 5.0 harness? pcm to injector harness, thanks, larry