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I have a 85GT 5.0 CFI and I just bought a 5.0EFI out of a 90GT and the full wiring harness.. For you guys who have done this.. How hard is it to change the wiring in these cars?? Should I attempt it or take it to a shop.. I have a decent aptitude about cars but have never rewired an entire car...

Any online guides or tips or anything availiable cause I have found none.

Any Helpful hints or advice is much appreciated :)

Thnx
 

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ok another question heh... will I have to rewire from tallights to headlights or from the computer on.. ie. dash, engine compartment? and what type of fuel system changes will I have to make besides the pump? Will I have to change all the lines?

Thnx again

Scott :eek:
 

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come on guys I know some of you know and the rest of ya have good guesses lol...
 

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As far as wiring goes, I have only removed the upper/lower intake from my 5.0, so I do not have the complete knowledge on the ins and outs of this swap. Saying this, if I was in your situation and wanted an HO motor, I would not hesitate to do the swap, especially since you have the wiring harness.

You are somewhat ahead of the curve in that your car already is fuel injected. The fuel tank is wired for an electric fuel pump and the car has the relays needed to make it work. Perhaps most of the emmissions components will be the same. (Oops, looking on that Bronco site, it appears the tank may not be set up for an internal fuel pump but that it may have an external pump. You could probably swap in a junkyard tank, even from a 4cyl 87 and up car.)

My suggestion would be to keep the 90 harness in one piece. Do not try to cut and modify it unless you are absolutely sure of what you are doing. I worked in a shop where we swapped out the blown-up inline 6 DOHC FI Cressida motor in the boss's girlfriends car. Unfortunately, he bought us a junkyard mill from a later year. The FI wiring was similar, but not quite the same. We should have used the old harness on the new motor, but it was easier to just plug the new engines harness into the old computer. Big mistake. The engine never did run right. Most of the connectors were the same, but a few were different. Another mechanic tried to graft the old harness to the new harness and thus destroyed the old harness. If I had to do that car again, I would have taken all the wiring off the new engine and connected the old harness to the sensors on the new engine.

Get a wiring diagram for a 90. My Haynes manual has a so-so wiring diagram. A color diagram would be better.

Become familiar with all the various sensors that the HO motor has. This will help you with the wiring since you will understand how it works. I understand all the connections are unique, so this will help when attaching the wiring. Know where the ground wires attach.

You could also look at the diagram for an 86 GT. Compare the wiring to the 90. The 86 chassis will be closer to your year than the 90s will. I bet you can do this without rewiring the whole car. You may want to get a pin description for the 90 computer and the 85 computer, so you will know which pins can be used with your current electric fuel pump wiring and power/ground wiring to the computer.

I think if you approach the project in an organized manner and are patient and have access to a running car in case you need to see how the wires are routed, I think you will have success.

Good luck. Tom
 
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