wiring harness for a 258 to 4.0 (top end) swap? - JeepForum.com
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post #1 of 24 Old 12-01-2016, 05:15 PM Thread Starter
jeepzjgrrl
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wiring harness for a 258 to 4.0 (top end) swap?

The harness and top end that is in my 86 CJ7 is from a 96 Cherokee. It's a wiring mess and I know something must be drawing power to kill my battery. Also the kid before me made a wiring mess. Pics below.

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Spaghetti Wiring

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post #2 of 24 Old 12-01-2016, 07:46 PM
Pathkiller
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What is your question? You can find wiring diagrams online, color coded, which tell you what is what.


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post #3 of 24 Old 12-01-2016, 08:05 PM Thread Starter
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Quote:
Originally Posted by Pathkiller View Post
What is your question? You can find wiring diagrams online, color coded, which tell you what is what.
Well my question is really what wires can I delete from this set up. And what might be drawing on the battery
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post #4 of 24 Old 12-01-2016, 10:44 PM
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The first thing I check when something draws current is the alternator, often a failure mode is to keep the field energized even with key off. Can check a couple ways, Wave a screwdriver close to it at the rear if it's on you'll feel a pull on the screwdriver because the field is energized and magnetic, feel the alternator when it's cool out and if the alternator feels warm after sitting for a while, it's staying on. If it's not the alternator, a good place to start is pulling a fuse at a time, if one changes the draw, you know what circuit to look at.

As Path said, you'll want a wiring diagram, possibly for both the CJ and the 96 cherokee so you can match up what changes were made and why on the 'new' harness.

What all was switched with 4.0? It should have been pretty close to a direct swap with only a few connections that would need to be changed around.

What all was swapped over with the 4.0? The old 258 harness should have been able to connect right with nearly everything on the 4.0
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post #5 of 24 Old 12-01-2016, 11:02 PM Thread Starter
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Quote:
Originally Posted by puppybreath View Post
The first thing I check when something draws current is the alternator, often a failure mode is to keep the field energized even with key off. Can check a couple ways, Wave a screwdriver close to it at the rear if it's on you'll feel a pull on the screwdriver because the field is energized and magnetic, feel the alternator when it's cool out and if the alternator feels warm after sitting for a while, it's staying on. If it's not the alternator, a good place to start is pulling a fuse at a time, if one changes the draw, you know what circuit to look at.

As Path said, you'll want a wiring diagram, possibly for both the CJ and the 96 cherokee so you can match up what changes were made and why on the 'new' harness.

What all was switched with 4.0? It should have been pretty close to a direct swap with only a few connections that would need to be changed around.

What all was swapped over with the 4.0? The old 258 harness should have been able to connect right with nearly everything on the 4.0
So when you go from a 86 to a 96 there is alot of change. I now have a PCM. EFI etc. There are alot of wires that go no where. I didn't do the swap so it's a figure out what the **** is going on. I already found wires that went nowhere but were live today. Check engine light, tachometer wire. Etc. I'm lost a bit.

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post #6 of 24 Old 12-01-2016, 11:45 PM
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That is definitely a mess. As a 1986 CJ you started with a lot of useless spaghetti under the hood anyway.

Any sign of the Cherokee main fuse box / power distribution centre that sits under the hood and feeds the power to the main bits? The common way of doing this conversion is to take the box and its harness and lay it on top of the CJ, which requires only a few wires to be hooked up (power, switched power and ground) to power the engine through the power distribution centre and then the sensor wires to be connected on to the engine, the coil wires and the fuel injection and the alternator wires. The only wires going to the interior from this harness should be for the Check Engine Light.

Those loose relays suggest they are either for the CJ bits (such as lights) or someone has butchered the main fuse box / power distribution centre from the Cherokee.

Now, if they had any sense they did not try to pull a 96 Cherokee wiring harness through the whole CJ so a good place to start is the CJ bulkhead connector. It is a large round plug in the firewall that connects the middle and rear of the CJ with the engine bay.

If this is intact I suggest eradicating all other wires through the bulkhead apart from the CEL for the 1996 harness. Even this I suggest you pull back out for the time being to keep it clean.

Now start with the basics. All the CJ wiring in the fuse box diagram below should still be there and you should have the headlights under control and indicators and horn, maybe a starter solenoid and feed from the alternator going back through a fusible link to the bulkhead connector and o to the ignition switch and fuse box. Check there is nothing butchered under the dash by referring to the wiring diagram (it is for a 1981 to 1983, but the dash panel back is about the same and I have drawn a line around what should be inside the cab to give you an idea of how they are seperated).

Go back to the bulkhead connector and chase where those wires go in the engine bay. You need lights, indicator, horn. Then identify what you have of the ignition circuit and how the starter solenoid and alternator are wired. You may find a lot of vaccuum hose and bits from the 1986 emissions control system is still there, all redundant.

- The alternator and its wiring needs to be identified. The Cherokee used the PCM to control the field, a CJ used an ignition feed. The alternator then connected to the solenoid on the CJ but the Cherokee connected to the PDC. The Cherokee used a Denso product, the CJ something more American.

- The starter also needs to be identified and how this is wired. The CJ used a solenoid, the Cherokee used a relay in the PDC. it is unlikely the starter has been changed so you need to identify how it is being powered, with a big solenoid or a relay.


Then report back on what you have.

The Cherokee FSM can be downloaded for free, I think at "Ol Collins Jeep" or something similar, I am sure someone will come in with e real address. If you open section 8 of the FSM, all the wiring schematics are in there.

I got the CJ FSM from civilianjeep.com and the wiring diagrams from somewhere.
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1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
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post #7 of 24 Old 12-02-2016, 05:53 PM Thread Starter
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Quote:
Originally Posted by BagusJeep View Post
That is definitely a mess. As a 1986 CJ you started with a lot of useless spaghetti under the hood anyway.

Any sign of the Cherokee main fuse box / power distribution centre that sits under the hood and feeds the power to the main bits? The common way of doing this conversion is to take the box and its harness and lay it on top of the CJ, which requires only a few wires to be hooked up (power, switched power and ground) to power the engine through the power distribution centre and then the sensor wires to be connected on to the engine, the coil wires and the fuel injection and the alternator wires. The only wires going to the interior from this harness should be for the Check Engine Light.

Those loose relays suggest they are either for the CJ bits (such as lights) or someone has butchered the main fuse box / power distribution centre from the Cherokee.

Now, if they had any sense they did not try to pull a 96 Cherokee wiring harness through the whole CJ so a good place to start is the CJ bulkhead connector. It is a large round plug in the firewall that connects the middle and rear of the CJ with the engine bay.

If this is intact I suggest eradicating all other wires through the bulkhead apart from the CEL for the 1996 harness. Even this I suggest you pull back out for the time being to keep it clean.

Now start with the basics. All the CJ wiring in the fuse box diagram below should still be there and you should have the headlights under control and indicators and horn, maybe a starter solenoid and feed from the alternator going back through a fusible link to the bulkhead connector and o to the ignition switch and fuse box. Check there is nothing butchered under the dash by referring to the wiring diagram (it is for a 1981 to 1983, but the dash panel back is about the same and I have drawn a line around what should be inside the cab to give you an idea of how they are seperated).

Go back to the bulkhead connector and chase where those wires go in the engine bay. You need lights, indicator, horn. Then identify what you have of the ignition circuit and how the starter solenoid and alternator are wired. You may find a lot of vaccuum hose and bits from the 1986 emissions control system is still there, all redundant.

- The alternator and its wiring needs to be identified. The Cherokee used the PCM to control the field, a CJ used an ignition feed. The alternator then connected to the solenoid on the CJ but the Cherokee connected to the PDC. The Cherokee used a Denso product, the CJ something more American.

- The starter also needs to be identified and how this is wired. The CJ used a solenoid, the Cherokee used a relay in the PDC. it is unlikely the starter has been changed so you need to identify how it is being powered, with a big solenoid or a relay.

Then report back on what you have.

The Cherokee FSM can be downloaded for free, I think at "Ol Collins Jeep" or something similar, I am sure someone will come in with e real address. If you open section 8 of the FSM, all the wiring schematics are in there.

I got the CJ FSM from civilianjeep.com and the wiring diagrams from somewhere.
I have a question for you, one wire going straight to the battery, (looks from) the jumbled mess on top you talked about and also a wire is bs spliced into same wire and going to an electric fan control box. The original wire goes from the battery over the engine and into the loom of relays etc pictured. But when I touch it to the pos side of the battery it sparks, which makes me think there is a ground issue. I wish I could take a video to show.

forumrunner_20161202_185153.jpg
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post #8 of 24 Old 10-02-2017, 12:33 PM Thread Starter
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so here is an update...and i am shocked that this isnt a question more people have...Painless wiring does not have a harness for this setup. remember its a 258(4.2l) bottom end with a 4.0l top end with fuel injection. and a 1996 Cherokee was the host for the harness and the top end. I need to just rewire the entire 86 CJ7 over again. i found where the grounded out pos wire is from the starter to the battery but i do not know how to properly rewire a starter from battery to starter and to ignition....does anyone know of someone in New Jersey that can help.
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post #9 of 24 Old 10-02-2017, 09:17 PM
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http://www.hesco.us/products/7902/40...6#.WdLxnEyZOT8

Hesco makes the kits for MOPAR. Here is a link to what you need, but it is not cheap. They also sell the individual parts. I bought parts from them about 20 years ago when I swapped in an entire 4.0 into my CJ.

From reading your posts, I think you are on the right track to find someone knowledgeable to help. Pointing them towards the Hesco website may help when it comes to finding parts.

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post #10 of 24 Old 10-09-2017, 07:45 PM Thread Starter
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Quote:
Originally Posted by schardein View Post
http://www.hesco.us/products/7902/40...6#.WdLxnEyZOT8

Hesco makes the kits for MOPAR. Here is a link to what you need, but it is not cheap. They also sell the individual parts. I bought parts from them about 20 years ago when I swapped in an entire 4.0 into my CJ.

From reading your posts, I think you are on the right track to find someone knowledgeable to help. Pointing them towards the Hesco website may help when it comes to finding parts.
Thank you, i sent them an email looking for a wiring harness for a 258 bottem end and 4.0 top. lets see what they come up with....i dont mind paying 500 bucks if it works they way it should. also i remember seeing a guy on one of these sites that says he can outfit a 4.0 wiring harness for the conversion and you ship him they Cherokee wiring harness and he will outfit it for the 258 and then send it back. havent been able to find it since.
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post #11 of 24 Old 10-10-2017, 01:47 PM
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Quote:
Originally Posted by jeepzjgrrl View Post
Thank you, i sent them an email looking for a wiring harness for a 258 bottem end and 4.0 top. lets see what they come up with....i dont mind paying 500 bucks if it works they way it should. also i remember seeing a guy on one of these sites that says he can outfit a 4.0 wiring harness for the conversion and you ship him they Cherokee wiring harness and he will outfit it for the 258 and then send it back. havent been able to find it since.
Sounds like you're talking about this.

http://www.hotwireauto.com/?page=sales-jeep

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post #12 of 24 Old 11-08-2017, 12:05 PM Thread Starter
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Originally Posted by firegod33 View Post

Sounds like you're talking about this.

http://www.hotwireauto.com/?page=sales-jeep
I sent them an email. Let's see if they can make a harness.
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post #13 of 24 Old 11-28-2017, 12:35 PM Thread Starter
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Originally Posted by jeepzjgrrl View Post

I sent them an email. Let's see if they can make a harness.
Update: They never emailed me back.
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post #14 of 24 Old 12-02-2017, 10:07 PM
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Quote:
Originally Posted by jeepzjgrrl View Post
so here is an update...and i am shocked that this isnt a question more people have...Painless wiring does not have a harness for this setup. remember its a 258(4.2l) bottom end with a 4.0l top end with fuel injection. and a 1996 Cherokee was the host for the harness and the top end. I need to just rewire the entire 86 CJ7 over again. i found where the grounded out pos wire is from the starter to the battery but i do not know how to properly rewire a starter from battery to starter and to ignition....does anyone know of someone in New Jersey that can help.
You will probably not find a wiring harness specifically for the 4.0L top and the 86 CJ-7 bottom. So far as I know, that unicorn doesn't exist. Also, that isn't what you need. You need a stand alone harness for the 4.0L and you need to clean up part of the original 86 harness. Don't get too hung up on having a 4.0L head on a 258 bottom end; it really doesn't matter as the differences between a full 4.0L swap and the 4.0L head only are minimal. Most any product intended to swap in a 4.oL will have everything you need (except maybe the alternator wiring). If you have the $$, a stand alone harness for the 96 engine is your best bet. Give Hesco a call and ask for a stand alone harness for a 1996 4.0L. They will also have instructions on how to splice that into your 86 so it doesn't look like it was attacked by the rat equivalent to Martha Stewart.

As for the rest, you will need to get a wiring diagram for the 86 and identify the circuits you must keep. The starter, oil pressure, and temperature are a few of the big ones. You won't need hardly any of the actual engine harness.

If you don't have the money for a stand alone harness, you will have to take the diagrams already attached to this thread and trace each wire, removing the ones not needed. Tedious PITA for sure.

Every 20 minute job is just one broken bolt away from a three day ordeal.
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post #15 of 24 Old 12-02-2017, 10:47 PM
justals
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I have the 258 block with 4.0 head on my 85 cj. Purchased the engine harness from hesco.
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