88 4.2L will not stop running - JeepForum.com
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post #1 of 16 Old 10-11-2021, 11:26 PM Thread Starter
KaiserRandy
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88 4.2L will not stop running

Hi All,

I have an 88 4.2L that will not turn off. I have started tracing the wires under the hood and found a large group of yellow wires with one brown (from Alternator) and one red (still trying to figure it out). I know there has to be a short for the key to be removed and power still flowing. Any thoughts on this? I will get pictures tomorrow.


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post #2 of 16 Old 10-12-2021, 06:24 AM
Chrisnvegas
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It's probably the alternator. It's backfeeding power to the ignition.

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post #3 of 16 Old 10-12-2021, 02:42 PM
timatoe
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Stock ignition system or something else? Did this just start happening or did you buy it this way?

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post #4 of 16 Old 10-12-2021, 08:02 PM Thread Starter
KaiserRandy
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I think its a stock system and it just started two days ago. I bought the Jeep in July, but have had issues from day zero. New carb, fuel pump (mechanical), filter, air cleaner, and I removed (after this issue started) the lighting to two extra lights that I didn't like. I have videos and pictures I am going to post as well.
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post #5 of 16 Old 10-12-2021, 11:45 PM Thread Starter
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I have two videos as well, but I cannot upload them. The red wire in the first picture below my palm is the one getting hot.
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PXL_20211013_012046080.jpg   PXL_20211013_012133696.jpg   PXL_20211013_012127664.jpg   PXL_20211013_012105461.jpg  

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post #6 of 16 Old 10-13-2021, 07:36 AM
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If it worked reasonably well before, what changed? If you hadn't done anything under the hood, my guess would be the ignition switch. Could be carbon tracking or some chunk of conductive crap that got pushed into connection when you turned the key. Find the harness plug under the steering column and pull it. If it shuts off you know that the short is on the key side of the harness.
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post #7 of 16 Old 10-13-2021, 10:49 AM
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Quote:
Originally Posted by vadslram View Post
If it worked reasonably well before, what changed? If you hadn't done anything under the hood, my guess would be the ignition switch. Could be carbon tracking or some chunk of conductive crap that got pushed into connection when you turned the key. Find the harness plug under the steering column and pull it. If it shuts off you know that the short is on the key side of the harness.
I'm gonna go with this as well, I'm not a hardcore wire guru or anything, but you've been messing with the wires, so if you had a wire touching another (short) or a wire that was barely holding on that cuts the system, the moving probably wouldve changed something?

Or, look for any loose wires that may have come undone in your engine bay.

The Ignition is fairly simple, beware of the rods inside, lol, go slow, take your time, buy a Chilton's book or something. That's what helped me get the rods back correctly. If you have patience, it's not hard. Hell, I did it.

And now I have a shiny new key!! Probbaly time for one anyhow.
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post #8 of 16 Old 10-13-2021, 10:50 AM
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Oh, one more thing, I have an 89 4.2, go with the nutter bypass.

Luckily the PO did it, but you can eliminate A LOT of those wires once done, making life a tad easier. The crap connections I found behind the clump of wires.... jeez, it's probably why they went Nutter, lol, easier than tracking down wires hidden in the sleeves.
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post #9 of 16 Old 10-13-2021, 03:40 PM
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Before you butch the harness, unplug the alternator and see it it shuts off. When the key won't shut the Jeep off, do the things that are easiest first. I think it's the diodes. Unplug the field plug. If it works, there's the problem.
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post #10 of 16 Old 10-13-2021, 05:07 PM
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Quote:
Originally Posted by Chrisnvegas View Post
Before you butch the harness, unplug the alternator and see it it shuts off. When the key won't shut the Jeep off, do the things that are easiest first. I think it's the diodes. Unplug the field plug. If it works, there's the problem.
I just dove into the schematics and yes. The alternator field circuits do splice into the same circuit that powers the ignition coil. If a diode is "leaking" it will provide a reverse voltage into the circuit. Unplug the easy plug on the alternator and see if it shuts off.

If not. Do you have a tilt column? If yes, does the column have play and can it be wiggled at the tilt area? If yes, this creates havoc on the rod adjustment from the cylinder to the ignition switch in the column.

The ignition switch contacts could be flaky. The ignition switch hole that the rod goes into could be worn. The lock cylinder can be worn and also the rack/sector gear in the column can be worn or even just binding due to old sticky grease. This caused problems on my 87. I would turn my key to start and would have to manually move the key back to run when I first got mine or the starter would stay engaged. . The lock cylinder would move back but not far enough. It was sticky. I took my column apart and cleaned and lubed everything and now it works like it was built in 2020 but the root cause was the rack and sector lube was worn out and might as well have been glue rather than grease.

EDIT: Schematically the splice that you show with all the yellow wires really belongs. I followed it through a few pages of different systems. I am not sure where the wire you say gets hot goes to but.... An alternator diode is used to convert AC current to DC. If a diode is messed up, you are now mixing AC and DC together. Without using a thousand words, this mix is not good. It could cause a wire to get warm.
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If you cannot fix it with a hammer then it has to be an electrical problem.
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post #11 of 16 Old 10-13-2021, 07:09 PM Thread Starter
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So I have switched the ignition switch already. New alternator is going on Friday, as the current has some corrosion. Have not tried disconnecting it, but the ignition switch disconnected had no effect. That's including the newer one.

Since it is already apart and half the dash removed, I'm going to remove the rest after work tomorrow and Friday spend the day checking all my wires and connections. I already found a few under the hood that are worn and could become issues later.

The wire I was referring to is red. It connects to a splice with a small yellow wire going to the ignition coil cover, green to the silver block on the firewall behind the battery (resistor block I think), and that red ran to the bundle of yellow wires. It is collecting the energy and getting hot, but is not the issue as I disconnected it and stl have energy. This also leads me to believe alternator.

I'm not installing the new one though until my full wire trace is done. I've already cleared the tail light harnesses and verified their operation up to the connection under dash.

I'm at a stop for now, as I'm too fat to be trying to be a contortionist...

Randy
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'88 4.2L "Rough Rider"
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post #12 of 16 Old 10-13-2021, 07:21 PM
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Quote:
Originally Posted by Chrisnvegas View Post
Before you butch the harness, unplug the alternator and see it it shuts off. When the key won't shut the Jeep off, do the things that are easiest first. I think it's the diodes. Unplug the field plug. If it works, there's the problem.
This, lol, I just did it to myself tonigt... gonna start a thread, but check this.
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post #13 of 16 Old 10-13-2021, 09:19 PM Thread Starter
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This is link to first video.


This is the second video.

These I do a walk-through of the issue. Only about 3 or 4 minutes in total. I'll do another when I get started tomorrow.

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post #14 of 16 Old Yesterday, 05:36 PM
gehlsurf
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Quote:
Originally Posted by KaiserRandy View Post

This is link to first video.


This is the second video.

These I do a walk-through of the issue. Only about 3 or 4 minutes in total. I'll do another when I get started tomorrow.
The vids are showing unavailable to me on my mobile.

Are they showing up for others? Might wanna check that.
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post #15 of 16 Old Yesterday, 05:52 PM
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Quote:
Originally Posted by gehlsurf View Post
The vids are showing unavailable to me on my mobile.

Are they showing up for others? Might wanna check that.
Not showing for me either, but that could be a firewall issue at work.

Quote:
Originally Posted by George Orwell
We sleep safe in our beds because rough men stand ready in the night to visit violence on those who would do us harm.
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