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-   -   1989 Wrangler, 4.2L Timing Chain failure (http://www.wranglerforum.com/f218/1989-wrangler-4-2l-timing-chain-failure-200629.html)

rjkeller 11-20-2012 01:49 PM

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?

OverkillYJ 11-20-2012 05:23 PM

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MellowYellow89YJ 11-20-2012 06:34 PM

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.

rjkeller 11-22-2012 10:45 AM

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!

jokerchief462 11-22-2012 01:49 PM

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.

MellowYellow89YJ 11-23-2012 10:57 AM

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. :)

rjkeller 11-26-2012 11:48 AM

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.

OverkillYJ 11-26-2012 12:26 PM

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.

darkproximity 11-26-2012 01:25 PM

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

mckinley4371 11-26-2012 03:51 PM

Can someone take a minute to explain what non-interference vs interference engine means? I've never heard this term before.

MellowYellow89YJ 11-26-2012 04:02 PM

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.

mckinley4371 11-26-2012 04:19 PM

Thanks Mellow!

CDennyRun 11-26-2012 04:32 PM

Quote:

Originally Posted by OverkillYJ (Post 3034562)
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!

Craigthemann 05-24-2013 11:51 PM

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?

jokerchief462 05-25-2013 12:39 AM

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.

bajajohn 05-25-2013 06:20 AM

Quote:

Originally Posted by Craigthemann (Post 3790959)
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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