push rod issue with 4.2l - JeepForum.com

 
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post #1 of 5 Old 01-10-2010, 04:14 PM Thread Starter
JimNut
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1986 CJ7 
 
Join Date: Apr 2009
Location: Michigan
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push rod issue with 4.2l

86 Jeep CJ-7 with a 4.2l

Jeep was running great yesterday like it has been for a few months now. Went out today to pull it into the garage to work on some lighting and as soon as it starts it is backfiring/popping through the carb.

First thing I did was a compression check which turned out good. (All cylinders within 5% or so and around 110 psi) Checked a few other things and then decided to pull off the valve cover to make sure I didn't have a broken valve spring or something and found this:




Looked a little further into it and the push rod is not bent,valve spring seems okay, rocker is good. My question is what would cause this? Only thing I can think if is a collapsed lifter or something along those lines. As of right now the only way to get the push rod back under the lifter is to loosen the rocker and re-adjust.

Should I just put it back together and see what happens? I have a trip this upcoming weekend so I really want to get this figured out..

Thanks for the help!


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post #2 of 5 Old 01-10-2010, 04:19 PM
Fjguercio
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1978 CJ7 
 
Join Date: Dec 2007
Location: Burnsville, MN
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if the push rod wears into the rocker and you see the wear pattern touch the hole in rocker... it will cover up the oil hole, no oil to rocker, it gets hot and not lubricated. That would be my guess.
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post #3 of 5 Old 01-10-2010, 05:04 PM
CJunk
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Location: Cape Cod
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Pretty sure over reving can also make that happen. Do that lately?
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post #4 of 5 Old 01-10-2010, 05:48 PM Thread Starter
JimNut
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Join Date: Apr 2009
Location: Michigan
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Quote:
Originally Posted by Fjguercio View Post
if the push rod wears into the rocker and you see the wear pattern touch the hole in rocker... it will cover up the oil hole, no oil to rocker, it gets hot and not lubricated. That would be my guess.
I'll definitely look into that! I just put the push rod back under the rocker and re-torqued everything and fired the motor up and everything seemed fine. Before I put the valve cover back on for good I will check that

Quote:
Originally Posted by CJunk View Post
Pretty sure over reving can also make that happen. Do that lately?
Nope. Yesteday I just moved it around in the backyard and today I went to pull it into the garage to work on a few other things. Good thinking though

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post #5 of 5 Old 01-10-2010, 10:04 PM
GeCJ7
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1984 CJ7 
 
Join Date: May 2009
Location: Spokane, WA.
Posts: 29
This happen to me, however I thought the reason was that my motor had high miles. I too just reinstalled it, but it drop out very soon after. I took to a engine mechanic and they replaced the lifter and rocker arm with a new one. After that, all was well. Before all this, I used to have a bad lifter knock from a cold start for many years. I figured that the lifter was on its last leg.
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