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Old 11-20-2012, 12:49 PM   #1
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1989 Wrangler, 4.2L Timing Chain failure

Hello all,

My mechanic just told me that the timing chain has failed on my 1989 Wrangler. It was being driven at the time and the engine just stopped running. The distributor is not turning. I think the distributor is gear driven off the camshaft. The big question is whether this engine is an interference engine. If not, I'll probably be OK with a new timing chain. If so, I'm looking at some major repairs if valves are bent. Has anyone ever experienced this before? Any recommendations?

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Old 11-20-2012, 04:23 PM   #2
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Old 11-20-2012, 05:34 PM   #3
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The JEEP 4.2, 4.0, and 2.5 are all non-interference designs.... Just make sure every thing is lined back up before you get the new chain on.
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Old 11-22-2012, 09:45 AM   #4
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Thanks MellowYellow. I'm really not trying to be rude, but are you SURE that it's not an interference engine? I've seen many posts suggesting both, which can't be true!
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Old 11-22-2012, 12:49 PM   #5
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All the research I have done says no interference so time to tear into it and repair whats broke. Once the timing chain is replaced you can tell. Just run a cold compression test to confirm the cylinders are good and if so run it if not take the head ooff and figure it out. Sounds like an easy fix.
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Old 11-23-2012, 09:57 AM   #6
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Quote:
Originally Posted by rjkeller
Thanks MellowYellow. I'm really not trying to be rude, but are you SURE that it's not an interference engine? I've seen many posts suggesting both, which can't be true!
Yes, I am sure.
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Old 11-26-2012, 10:48 AM   #7
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Hello all,

I wanted to send a quick update on my Wrangler situation. Thanks to the input from all of you, I made my mechanic pull the valve cover so we could observe the valves while turning the cam. He even agreed not to charge me for that additional labor if the valves were intact. He just called to tell me that he's embarrassed for recommending a new engine. Valves are completely fine and compression is very good. He's finishing it up now. Your advice here saved me thousands of dollars. Many thanks to all. I hope I can be as helpful to others over time.
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Old 11-26-2012, 11:26 AM   #8
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So according to this thread, if my timing chain ever breaks I can just line up the marks on the gear and pop a new one on. Would be good as new correct? What if it were to jump time? Just dont drive it until I can fix it and it will be ok, or would that damage it immediatly? I ask because I had a truck crap out on me after jumping time years ago.
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Old 11-26-2012, 12:25 PM   #9
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It would run like crap if it skipped time, but because it's a non interference motor, the valves would never be in a position that the pistons would make contact with them if the timing chain broke
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Old 11-26-2012, 02:51 PM   #10
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Can someone take a minute to explain what non-interference vs interference engine means? I've never heard this term before.
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Old 11-26-2012, 03:02 PM   #11
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Quote:
Originally Posted by mckinley4371
Can someone take a minute to explain what non-interference vs interference engine means? I've never heard this term before.
In a non interference motor, the valves do not hang into the cylinder when open and are never in a position that would make contact with the pistons.... Even with a broken timing set.
In an interference motor, the valves hang low into the cylinder when open and are in a position to contact the piston if the cam and crank get out of sync.
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Old 11-26-2012, 03:19 PM   #12
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Thanks Mellow!
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Old 11-26-2012, 03:32 PM   #13
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Quote:
Originally Posted by OverkillYJ View Post
So according to this thread, if my timing chain ever breaks I can just line up the marks on the gear and pop a new one on. Would be good as new correct? What if it were to jump time? Just dont drive it until I can fix it and it will be ok, or would that damage it immediatly? I ask because I had a truck crap out on me after jumping time years ago.
Just make sure to change it before it gets loose enough to jump time and or fail. It really isn't a hard job, and not very time consuming. AMC made it pretty simple for us!
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Old 05-24-2013, 10:51 PM   #14
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I am having a similar problem. I want to simply replace my sloppy timing chain with a new set and found that the timing marks don't line up so I am scared to take it off. It runs fine, as far as I can tell, this is my first Jeep. With #1 cylinder at TDC the crank gear timing mark is perfect but the cam gear is 180* off minus one tooth. Can the engine run fine like this, should I leave it alone. I want it to be right and every shred of information out there says that the marks must line up. What should I do here?
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Old 05-24-2013, 11:39 PM   #15
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Check your original thread I posted a page from the FSM in there with the instructions for the install. Just line it up forget the #1 TDC comment.
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Old 05-25-2013, 05:20 AM   #16
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Originally Posted by Craigthemann View Post
I am having a similar problem. I want to simply replace my sloppy timing chain with a new set and found that the timing marks don't line up so I am scared to take it off. It runs fine, as far as I can tell, this is my first Jeep. With #1 cylinder at TDC the crank gear timing mark is perfect but the cam gear is 180* off minus one tooth. Can the engine run fine like this, should I leave it alone. I want it to be right and every shred of information out there says that the marks must line up. What should I do here?


It may run but I bet it will run a whole lot better if the chain is installed properly

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