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Discussion Starter · #1 · (Edited)
first timer here so go easy on me. Long story short, I hurt the original motor which was a great 1988 Renix 4.0. A buddy had a 1996 sitting around so I decided to put it in my XJ.

Keep in Mind that this is a trail only rig (not street legal)

So here is the problem. After swapping new motor it ran for a few afternoons while I deleted the smog set up for more room in the engine bay. THIS IS A TRAIL RIG ONLY ;) I know people will beat me up over this but I have lost spark on 3 & 4. I have great compression and I have replaced all the electrical components that I can-plug wires, coil, distributor, plugs, and what ever else I am missing. If you can help me please do. This project took over my life for awhile and then I had to put it aside. PLEASE HELP?
 

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Discussion Starter · #3 ·
What exactly are the smog related thingys you removed? Any possibility you disturbed something while doing that?
I removed all of the smog stuff. But it was running after I removed it. It’s not motor related it has to be electrical related. I have spark at 1,2,5, and 6
 

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Discussion Starter · #4 ·
I removed all of the smog stuff. But it was running after I removed it. It’s not motor related it has to be electrical related. I have spark at 1,2,5, and 6
Will a 4.0 stop sparking because of something I removed? I would think it would spark no matter what just wouldn’t run good because of vacuum leaks.
 

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Discussion Starter · #6 ·
I was kinda asking what is the smog stuff you removed 😂

Well anyway: are you sure there is no spark, or can this be a case of no or insufficient fuel to cyl. 3 & 4? External symptoms would be the same.
It is definitely no spark at all on 3 and 4. Because I am ignorant when it comes to engines I could not tell you all I removed. I was working with a rock crawler buddy on illuminating everything not needed on the trail. Also half the items that were with the 96’ motor would not plug and play with the 88’ stuff.
The research shows that 3 & 4 are opposite of each other in the coil pattern. I have replaced all the electrical stuff that I can. I have went through all the grounds that I could find even soldering the main harness where connections were junk.
 

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Sorry to keep repeating myself, but you actually have visual confirmation that other coils "fire" and give spark, but 3 and 4 give no visible spark when the engine is turning?

It could be that this is just a random event, where either 3 or 4 failed, maybe short circuit, and burned the coil next to it by chance. Can you see any hairline crack on the surface of the coil pack? Coil packs are very sensitive to moisture, so if there are any cracks in the surface, it might be burnt.
 

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Discussion Starter · #8 ·
Sorry to keep repeating myself, but you actually have visual confirmation that other coils "fire" and give spark, but 3 and 4 give no visible spark when the engine is turning?

It could be that this is just a random event, where either 3 or 4 failed, maybe short circuit, and burned the coil next to it by chance. Can you see any hairline crack on the surface of the coil pack? Coil packs are very sensitive to moisture, so if there are any cracks in the surface, it might be burnt.
Remember this is a 1988 Renix system. It has a coil and an ignition module which is all brand new and replaced twice. This Jeep has been in the shop for over a year now so no weather has touched the new parts.
Do you think trying to reindexing the distributor would help?
And yes I have confirmed no spark by taking each plug out and grounding it and only 3 and 4 has no fire. I even laid all 6 out one evening and turned engine over. Keep asking questions. That’s the only way I will fix it.
 

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Ah so the coil is common for all the plugs, not as in like Saab Trionic (which also dates back to the 80's) that has a separate integrated coil for each cylinder), my mistake.

I do not think the distributor indexing is the fault. Even if it was indexed wrong, it should give spark to 3 & 4, but at a wrong time.

I'm not familiar with the internals of the said distributor, so can't really say if and how it could be bust. If it is of a "traditional" kind, there could be a mechanical fault there, wear and tear, that would cause the coil not to fire for 3 & 4.
 

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Discussion Starter · #10 ·
Ah so the coil is common for all the plugs, not as in like Saab Trionic (which also dates back to the 80's) that has a separate integrated coil for each cylinder), my mistake.

I do not think the distributor indexing is the fault. Even if it was indexed wrong, it should give spark to 3 & 4, but at a wrong time.

I'm not familiar with the internals of the said distributor, so can't really say if and how it could be bust. If it is of a "traditional" kind, there could be a mechanical fault there, wear and tear, that would cause the coil not to fire for 3 & 4.
Mechanical wear on what? Any ideas? I just need a new view point to check a different area.
 

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Mechanical wear on what? Any ideas? I just need a new view point to check a different area.
Check out some cutout pics for distributors,the working principle of the mechanical ones is pretty much the same all around. There's a spinning arm that sends the spark to a proper wire at a time, and a sort of a cam and lobe (sorry, english not my native language so terminology is shoddy), that will open and close a cirquit to make the coil fire. There may be something broken there.
 

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Discussion Starter · #14 ·
Check out some cutout pics for distributors,the working principle of the mechanical ones is pretty much the same all around. There's a spinning arm that sends the spark to a proper wire at a time, and a sort of a cam and lobe (sorry, english not my native language so terminology is shoddy), that will open and close a cirquit to make the coil fire. There may be something broken there.
Thank you
 

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If you are getting spark on 4 of the cylinders then I think your ecu, coil, etc should be good. Initially I would think you have a dist cap problem, a crack? But you said you replaced the distributor, I assume it came with a cap?
I cannot remember the years but back then there was a procedure for indexing the distributor. There was a tsb were you cut a hole in the cap and used a multi-meter to verify where it was. If i remember correctly the spark would cross fire inside the cap. I wonder if your distributor has shaft or bushing play and not delivering the spark? This would be more so of a problem with the distributors that were not adjustable. quite a few years they were pinned into place.
if you pull your cap off you should only be able to move your rotor a max of 1/8 inch.
 

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Discussion Starter · #16 ·
If you are getting spark on 4 of the cylinders then I think your ecu, coil, etc should be good. Initially I would think you have a dist cap problem, a crack? But you said you replaced the distributor, I assume it came with a cap?
I cannot remember the years but back then there was a procedure for indexing the distributor. There was a tsb were you cut a hole in the cap and used a multi-meter to verify where it was. If i remember correctly the spark would cross fire inside the cap. I wonder if your distributor has shaft or bushing play and not delivering the spark? This would be more so of a problem with the distributors that were not adjustable. quite a few years they were pinned into place.
if you pull your cap off you should only be able to move your rotor a max of 1/8 inch.
This is something I can work with. Thank you.
 
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