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JoeyT 06-29-2013 12:54 PM

4.2 to 4.0 swap
Hi all.. I searched, but could not find what I am looking for. This may be due to my inability to search:)

I have an 89 YJ, 4.2 stick. I was given a 91 YJ, 4.0 HO Sahara. I swapped the engines, kept the 4.0 harness. I am at the point where I need to start hooking up the harness.

Does anyone know exactly what needs to be done here? The pass through connector than on my 4.2 went to the PCM, what does it connect to on the 4.0? I don't have the donor car here any longer, but do have access.

In short.. has anyone done this swap and they have the notes on harness pinouts? I can move the pins around on the external harness to my hearts content, I do not care about the warning lights but do want the dash to work ( tach and gauges...)

JoeyT 07-01-2013 01:39 PM

And.. for the archives.. I decided to pull the entire harness out of the donor YJ and swap the whole harness inside and out. The pinout in AllData was incorrect for the donor jeep, so instead of dicking around, I yanked the harness.

Also of note.. the 89 4.2 and 91 40 gas tanks are different. The 4.0 tank is larger, and the pump/sending unit does not fit in the 4.2 tank.

This swap is really best done with the donor vehicle on hand. The input shaft was different between the two, the pilot bearing on the 4.0 was assploded, and there are plenty of little issues. Of course, now I need to replace that front frame rail...

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