Complete yj swap

[Jeeperscreeper]

I'm sure this is on here but can't find it so sorry if a repost. But.....

 

I'm doing a full swap from a 92 wrangler. Motor(stroked) tf999 and np231 from the yj. I'm stuck on wiring. The yj bulkhead handles everything different. Or maybe I'm overthinking it. So I thought to swap in the yj fusebox and dash wiring.(a plus because it was all basically brand new when I got it and the mj fusebox doesn't look to good). Well now I'm at an issue of making all the electronics work. I was just Gunna dash swap and column swap as I have a full donor. But my issue is with lighting. Heater. Blower motor. Wipers(easy) and such. Am I just causing more of a headache than worth? Can the yj bulkhead just plug into an mj fusebox? Funds are tight. Was planning on doing this swap when I was more prepared but blew the renix as it's my daily and stuck. Anyone else use a yj engine harness? Or am I better off getting a xj harness for inside and out to rid of dummy lights

[Pete M]

there's a reason why you won't find many YJ/TJ to MJ/XJ swaps.  they are way harder because the vehicles share everything, but nothing at the same time.   An XJ harness will go a long way towards simplifying your life. 

[Jeeperscreeper]

Thanks. That's what it's looking like. I was hoping there was a way I could just splice the heater and lights and such into the yj fosebox and just use what I have as getting to yards isn't easy for me

[Jeeperscreeper]

Thanks. That's what it's looking like. I was hoping there was a way I could just splice the heater and lights and such into the yj fosebox and just use what I have as getting to yards isn't easy for me

[Jeeperscreeper]

19 minutes ago, Pete M said:

there's a reason why you won't find many YJ/TJ to MJ/XJ swaps.  they are way harder because the vehicles share everything, but nothing at the same time.   An XJ harness will go a long way towards simplifying your life. 

Do you know if xj engine harness would fit the yj motor without a headache?

[Eagle]

What year MJ?

 

You can make anything work -- it's a question of how much you want to make it happen.

 

For what it's worth, the Mopar Performance Catalog used to sell the '94 Wrangler injection/ignition system as a stand-alone package. It was intended for upgrading the early, carbureted YJs to fuel injection but, since it was stand-alone, that tells us that you should be able to run the engine harness from a '92 YJ as a stand-alone, and not have to mess with the chassis and under-dash harness of the MJ.

 

[Jeeperscreeper]

19 minutes ago, Eagle said:

What year MJ?

 

You can make anything work -- it's a question of how much you want to make it happen.

 

For what it's worth, the Mopar Performance Catalog used to sell the '94 Wrangler injection/ignition system as a stand-alone package. It was intended for upgrading the early, carbureted YJs to fuel injection but, since it was stand-alone, that tells us that you should be able to run the engine harness from a '92 YJ as a stand-alone, and not have to mess with the chassis and under-dash harness of the MJ.

 

It's a 90 mj. I just want basics. Bare bones. All lights. Wipers. Heat and guages but I was just going to use the guages as I have all the sensors. Just have to figure out fuel

[Pete M]

I wonder if you can splice in wiring to make 91+ XJ gauges work?

[Jeeperscreeper]

3 minutes ago, Pete M said:

I wonder if you can splice in wiring to make 91+ XJ gauges work?

That's kinda what I'm getting at. Like heater and lights and wipers i can basically splice the fuseboxes and make that work. Just take the wiring for it out of the mj box and replace it with the yj box. Maybe some h.o xj guages as mine are dummy lights. Basically it was one of those 'while I'm here's and it's spiraling out of control lol just wasn't sure if it was actually doable so I came here for insight. It would be cool to make it all appear stock. Will it be easy? Hell no. Doable? Eehhhhh

[Pete M]

seems like an afternoon in a junkyard with an HO XJ would help immensely.  

[Jeeperscreeper]

It would. But why take all the @#$% out of it. People claim they have done it but have yet to see a write up.

[Pete M]

I know it's common to go in the other direction, swapping easily-available XJ stuff into either 2.5 or 4.2 YJs, but off the top of my head I can't think of someone that actually went through with a YJ-into-XJ swap.    But that doesn't necessarily say much because my brain sucks.  So I go to google a lot, and on this particular effort I get TONS of XJ-into-YJ that floods the results.    I've not yet found anything useful for ya. 

[Eagle]

I still don't understand why there's a need to change anything besides the actual engine harness.

 

[Jeeperscreeper]

4 hours ago, Eagle said:

I still don't understand why there's a need to change anything besides the actual engine harness.

 

Because the yj handles the the bulkhead connector differently. It runs everything to the bulkhead plus sensors where as the mj/ splits off in the engine bay. Unless I'm just over thinking this. My search is the same. Everyone put xj in yj. So I Wana see if anyone has done this or has insight on wiring. I could just be over thinking it. I could be wrong. I'd also like to know 100% before I just start connecting and frying things. I'm not bad with electrical but I like to know what I'm doing is right before I burn it down ect

[Eagle]

1 hour ago, Jeeperscreeper said:

Because the yj handles the the bulkhead connector differently. It runs everything to the bulkhead plus sensors where as the mj/ splits off in the engine bay. Unless I'm just over thinking this. My search is the same. Everyone put xj in yj. So I Wana see if anyone has done this or has insight on wiring. I could just be over thinking it. I could be wrong. I'd also like to know 100% before I just start connecting and frying things. I'm not bad with electrical but I like to know what I'm doing is right before I burn it down ect

 

So get the wiring diagrams for both and adapt.

 

To reiterate: Jeep sold the '94 4.0L Injection/ignition setup as a stand-alone conversion for the older 4.2L Wranglers. That means the engine harness can be used completely independent from anything else in the chassis harness, so IMHO it doesn't make any sense to change things that don't need to be changed.

[Pete M]

do we know if that's the case?  are we sure that the 4.2L harness wasn't a "special" harness?

 

either way, with the correct diagrams anything is possible  

[Jeeperscreeper]

32 minutes ago, Eagle said:

 

So get the wiring diagrams for both and adapt.

 

To reiterate: Jeep sold the '94 4.0L Injection/ignition setup as a stand-alone conversion for the older 4.2L Wranglers. That means the engine harness can be used completely independent from anything else in the chassis harness, so IMHO it doesn't make any sense to change things that don't need to be changed

So It should just be plug and play to everything. I would just have to wire in blower motor and wipers ect as those are on engine side of mj

 

And I have wiring diagrams. But not positive on approach. I was going to take the fusebox and put the mj interior wires in but like I said electrical isn't absolutely strong for me. I have basic understanding but I Wana do this correct

[Eagle]

2 hours ago, Jeeperscreeper said:

So It should just be plug and play to everything. I would just have to wire in blower motor and wipers ect as those are on engine side of mj

 

 

They are on the engine side of the firewall, but they are not part of the engine harness. I don't understand why you need to "wire them in," since they are already wired in and ready to go.

 

You have a '90, so it originally had the ECU computer under the dashboard, but it did not have the C101 connector on the upper firewall (engine side). The new ECU should be mounted in the engine compartment, hopefully on the inside of the driver's side fender where it would be on a '91 or '92 MJ. So you'll have some wires going through the firewall that will be abandoned (or you can remove them to reduce clutter and confusion).

[ghetdjc320]

When I did a 4.0 HO swap in my 88 YJ i used a 95 XJ harness. The bulkehead connector splits into two sections. Look up “5 wires to fire” in YJ threads and you’ll see plenty of swaps using XJ harnesses. As has been mentioned, try to keep your engine harness as “stand-alone” as possible. 

[Jeeperscreeper]

5 hours ago, Eagle said:

 

They are on the engine side of the firewall, but they are not part of the engine harness. I don't understand why you need to "wire them in," since they are already wired in and ready to go.

 

You have a '90, so it originally had the ECU computer under the dashboard, but it did not have the C101 connector on the upper firewall (engine side). The new ECU should be mounted in the engine compartment, hopefully on the inside of the driver's side fender where it would be on a '91 or '92 MJ. So you'll have some wires going through the firewall that will be abandoned (or you can remove them to reduce clutter and confusion).

 

So your suggesting useing the mjs original renix engine harness? How would that work with the simplified ignition system and sensors of the h.o?

[Jeeperscreeper]

46 minutes ago, ghetdjc320 said:

When I did a 4.0 HO swap in my 88 YJ i used a 95 XJ harness. The bulkehead connector splits into two sections. Look up “5 wires to fire” in YJ threads and you’ll see plenty of swaps using XJ harnesses. As has been mentioned, try to keep your engine harness as “stand-alone” as possible. 

Iv been looking into that but I would just have to do it backwards correct? As it would be yj engine harness and mj dash harness

[ghetdjc320]

12 minutes ago, Jeeperscreeper said:

Iv been looking into that but I would just have to do it backwards correct? As it would be yj engine harness and mj dash harness

Yep that’s right. Just focus on the 5 to fire and leave the rest of the wiring alone. If you are electrically inclined, you can thin out the harness to a stand alone setup

[Jeeperscreeper]

8 minutes ago, ghetdjc320 said:

Yep that’s right. Just focus on the 5 to fire and leave the rest of the wiring alone. If you are electrically inclined, you can thin out the harness to a stand alone setup

Awesome. That's kinda what I was looking for. Then I can use xj dash harness to rid idiot lights. Do you know if the sensors will work from the yj. As long as I did 91-95 gen one h.o guages

[Eagle]

8 hours ago, Jeeperscreeper said:

 

So your suggesting useing the mjs original renix engine harness? How would that work with the simplified ignition system and sensors of the h.o?

 

No, I'm suggesting exactly the opposite. I'm suggesting using the '92 YJ engine harness to run the engine, and leaving everything else alone. If Chrysler can separate out the HO engine harness and sell it as an aftermarket upgrade for the 4.2L, there's no reason why you can't use it as a stand-alone. I just don't understand why you seem to be fixated on messing with wiring that isn't part of the engine harness.

 

"If it ain't broke ... don't fix it."

[ghetdjc320]

9 hours ago, Jeeperscreeper said:

Awesome. That's kinda what I was looking for. Then I can use xj dash harness to rid idiot lights. Do you know if the sensors will work from the yj. As long as I did 91-95 gen one h.o guages

I’d recommend you not try to use the HO harness for your gauges. It can be done but it’s not as straight forward as it would seem. 92-95 YJs used different gauges than the earlier gen even though 91-95 is the 4.0 HO. Essentially, you just want the new HO ecu to just run the fuel injection and ignition. here is what the ecu needs to run (I may be missing one or two items)

 

CPS signal from flywheel (or hesco crank dampener cps kit like Mopar used to use on the retrofit kit)

 

CTS from the thermostat housing

 

cam signal from distributor

 

constant and switched power

 

VSS From transmission or transfer case depending on 2wd or 4wd.

 

Your old harness will connect to your oil pressure sender and CTS on the back of the head. Just don’t try to integrate the HO harness into anything more than running the engine. If you decide to clean up the harness, you can strip out a great deal of wiring and simplify it down to stand alone just to run the engine.