4.0 Swap Question: Caution Electrical!!

Well, I knew it was going to happen.
The 4.0 in my 1990XJ finally expired... so I'm gonna drop in the 1994 4.0 paitently waiting in the garage. (nice how that happens, aint it)

Needless to say I'm not worried about the mechanical side I just have a few concerns (yes, I searched the archives) and I know that the "braintrust" is here @ !

I have the harness and computer from the 94 (all diligently removed from my old CJ), the problem is that I had to modify the section of harness to connect it to the old bulkhead. (essentially I converted from 94 to 83, and ran the remainder directly through the firewall.) I'm not sure if I'll even need that section of harness at all.

Questions:
Will the "engine harness" from the 94 simply plug into the "bulkhead to engine section" of the 90?
If not, must I match years exactly to replace the "bulkhead to engine" section? (ie. knowing 91-96 engines were all the same type do the harnesses match?)
If I must replace this section, will I need to replace the bulkhead?

I'm sure somebody here has already done this or something similar. Needless to say, any additional info regarding this is appreciated.

No. By far the easiest and probably the cheapest is to hit a pull-n-save and harvest the complete harness, including the dash harness. It will save you a lot of hassle and time. I'm and EE and have done more than my share of patching harnesses, but the Renix to HO conversion entails a ton of revamping and there is no way I would want to try and cobble a harness together.

Another option would be to swap intakes and keep the Renix system. Personally I like the Renix system and would keep it.

old_man said:

No. By far the easiest and probably the cheapest is to hit a pull-n-save and harvest the complete harness, including the dash harness. It will save you a lot of hassle and time.

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How far into the dash? I assume this would include bulkhead, fuseblock, etc? Would I be able to salvage ignition, cruise, a/c, fans, acessories? I'm not looking at a wiring diagram at the moment and only have FSM for the 90 here... the 94 FSM is in Illinois in a box.

old_man said:

Another option would be to swap intakes and keep the Renix system. Personally I like the Renix system and would keep it.

Click to expand...

I just searched this topic (and will be doing more, believe me) so I, hopefully, don't sound completely idiotic... but here goes. It appears I can utilize the entire 94 engine (block, head, manifolds, throttle body, injectors) sans "engine electrical" with minor mods to the TPS... or am I oversimplifying this? Considering that this engine (the 94) ran flawlessly, with the Renix should I expect similar performance? It has like 6K miles on the rebuild w/lifted cam and slight overbore.

I totally appreciate the assistance! I have no issue with the electrical as far as making thing work in a clean, consistant way. I am hoping to salvage as much as possible from what I have. Time is also an issue so I may just follow the latter and keep the Renix.

As far as the dash electrical, you would pull the whole elecrical harness. It isn't that hard. Just pull the dash and everything is easy. All in all, I would do the intake swap and call it done. Its a lot less hassle.