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Rewiring & Aftermarket ECU


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As with several others on the forum, the previous owners of my MJ spliced quite a bit as they did a 91 XJ interior swap and added accessories. Add on top of that a corroded fuse panel, flaky wiper controls, lack of back lighting for the gauge cluster, no interior lighting, etc  I'm coming to the conclusion that rewiring the vehicle is going to be inevitable. Needs also to support accessories such as an onboard air compressor and additional lighting (it's going to be used primarily as an off-road rig but still needs to be street legal).

 

If I'm going to put in the effort, replacing a 30-year old wiring harness with another used 30-year old wiring harness doesn't seem to make sense.  Does anyone have experience or recommendation using one of the Painless harnesses? eg http://www.painlessperformance.com/webcat/10202?

 

And if I'm tearing out the wiring harness, it's probably a good time to do an aftermarket ECM/ECU. Does anyone have a suggestion? Maybe something that's compatible with a digital dash like  https://www.4wd.com/p/superchips-trail-dash-2-42051/_/R-BGND-42051 ?

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22 minutes ago, LittleBoJeep88 said:

As with several others on the forum, the previous owners of my MJ spliced quite a bit as they did a 91 XJ interior swap and added accessories. Add on top of that a corroded fuse panel, flaky wiper controls, lack of back lighting for the gauge cluster, no interior lighting, etc  I'm coming to the conclusion that rewiring the vehicle is going to be inevitable. Needs also to support accessories such as an onboard air compressor and additional lighting (it's going to be used primarily as an off-road rig but still needs to be street legal).

 

If I'm going to put in the effort, replacing a 30-year old wiring harness with another used 30-year old wiring harness doesn't seem to make sense.  Does anyone have experience or recommendation using one of the Painless harnesses? eg http://www.painlessperformance.com/webcat/10202?

 

And if I'm tearing out the wiring harness, it's probably a good time to do an aftermarket ECM/ECU. Does anyone have a suggestion? Maybe something that's compatible with a digital dash like  https://www.4wd.com/p/superchips-trail-dash-2-42051/_/R-BGND-42051 ?

There is no aftermarket ECM/ECU, there is no support, there is no integration, no digital dash. 

 

That Painless is universal, will supply power the to ECM/ECU but is not an engine harness, IOWs, it ain't really a fit ALL your needs harness. 

 

Many of us have gone through our electrical and cleaned it up, new wire, new-er fuse block, new connectors..........etc.

 

But, if you want to spend the money- here's a how to, a fresh one-

 

Before the really smart guys say......That's not an MJ......no, it's not. 

It's the same harness, same fuse block, same bulkhead, same work and effort. 

 

 

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Painless has a custom shop that's little known to exist, but you need more than just that!
I worked on a project years ago where the owner requested a complete working drive train, and accessory swap from a 89 mustang Cobra to his early 40s Ford business sedan.
The easiest solution was to get painless wiring, ice aftermarket HVAC, the auto techs, fab guys, and horizon electronics custom PCMs together and sort the details.
We did what he ask, but the cost was astronomical!
Most people use the painless harness kits to power an aftermarket universal FCM, or ECM.
Atomic, FiTech, Holly, Squirt, and AEM all make universal 6cyl EFI kits. They would be an improvement to carburetors, but it's not a cheap adventure to take. You need some mechanical skill, and computer technical skills beyond the average hobbyists, or average mechanic.

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  • 3 weeks later...

@Jeep Driver thanks for the suggestion! I ended up going with the Speedway Motors version but the same idea:

 

https://www.speedwaymotors.com/Speedway-Universal-22-Circuit-Wiring-Harness,229874.html

 

@GreasemonkeySC yeah, not ideal from a cost perspective. but given that fuses (and windshield wiper circuit breakers) were so corroded that I couldn't even get them out without breaking off the prongs, I see it as a longer term investment in the vehicle (and my sanity). I tried tracking down an aftermarkert universal FCM or ECM but have been having trouble identifying which model will work with the 6cyl. lots of easy FI kits to convert from carb to fuel injected throttle body, but nothing that I could verify would work with the multiport GM 4.0L 6cyl varieties of engine. Any more specifics would be greatly appreciated.

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58 minutes ago, LittleBoJeep88 said:

 

I see it as a longer term investment in the vehicle (and my sanity). I tried tracking down an aftermarkert universal FCM or ECM but have been having trouble identifying which model will work with the 6cyl. lots of easy FI kits to convert from carb to fuel injected throttle body, but nothing that I could verify would work with the multiport GM 4.0L 6cyl varieties of engine. Any more specifics would be greatly appreciated.

 

WHOA!

 

The Jeep 4.0L engine is NOT a GM engine.

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