Gen 1 Dash wiring into 4.0L Harness

[Hitchner2009]

Hey guys, so I'm getting ready in spring to do my 4.0 swap with the 2.9. I'm keeping the gen 1 dash instead of swapping in the gen 2 dash, just don't want to throw more money at it. This project started in march. So I'm trying to find someone that has already written what does what on the 2.9l dash and what to splice it into on the 4.0l engine harness. Like color codes and what they run and what to splice into. Any help would make this so much easier, I'm working as a tech and going to tech school 6 days a week lol. I also wanted to know about the fuel line mods you had to do for the 4.0l, I noticied the fittings that go from the rail to the fuel filter are differant on the 2.9 and 4.0.

 

[adsm08]

I just did this, and it isn't that involved, it's just time consuming.

There wasn't much in the way of splicing, I just repinned an 89 dash harness to the gen 1 connectors. The important plugs are almost the same already.

The plugs for the cluster are a little different, but the wire end pins are the same. You just have to take them out of the later shells and put them in the older ones, I can get a pic of what it should look like. Same goes for the HVAC head. HVAC wire colors didn't even change.

Headlight switch, ignition switch, radio are all the same. Door dinger is too, if you care to keep it, but it is in a much different spot.

Turns and wipers were pretty different and the washer function wiring is really different, had to re-run some wire for that one.

Fuel lines were easy, I got some spring-lock fittings, clipped the 4.0's rail lines off near where the 2.9's FPR was, put the fittings in, and plugged into the existing fuel lines.



The biggest thing that had me confused on putting the gen 2 dash harness on the early dash was getting the gas and temp gauges working. At the ignition switch plug there is a big black and green wire with a little black wire, you need to take that and put it into the gen 2 harness. It's a 9 ohm resistor wire that is needed to get the voltage right for those two. If you don't use it you burn the circuit board.

 

[Hitchner2009]

So repinning if I have read it correct before means switching the plastic connectors from a wire harness with another type of plastic connector? Would you be able to tell me how to do that, seems a little involved. Problem solving isn't too hard for me, as I deal with this on a daily basis at the shop. But I don't want to get everything installed and turn the key and something isn't working haha.

 

[adsm08]

You are correct.

Run to the junk yard, pick up an 89 to 92 dash harness, engine doesn't matter, and get a straight pick and a seam ripper. If you can get the OEM wiring books, that is helpful too.


Like I said, I have done this, somewhat successfully (I don't have blower speed 2, and I am not sure why yet) and I have found and fixed the biggest issues from when I did it and I'm willing to help others get it figured out too. Once I got over the size of the project I realized that it really was pretty straight forward.