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Unread 02-27-2013, 07:39 AM   #16
86cj74.2L
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A jumped tooth will effect cranking pressure.


Easy to check and only costs you a gasket for your troubles.

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Unread 02-27-2013, 07:45 AM   #17
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Yeah I have been thinking of pulling the timing cover to check it. Just yesterday I said that a friend practically begged me not to do it. He said you will open up a whole new can of worms! Which ones? The ones that will be the solution?
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Unread 02-27-2013, 07:48 AM   #18
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Is it really as simple as removing the timing cover and inspecting the chain and alignment of the gears? If the gears are off one tooth, can you simply turn one of them to the right spot and replace the chain, or most likely a new chain?
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Unread 02-27-2013, 08:42 AM   #19
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A stretched chain is about the only thing that would cause it to jump a tooth.

You can check for chain stretch, without removing the timing cover, by noting how many degrees the crank can be turned from TDC before the distributer rotor moves.

If you can rotate the crank more than 10 degrees before the rotor moves, your chain needs to be replaced. The procedure is spelled out well in the Haynes manual.

Good luck,

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Unread 02-27-2013, 09:01 AM   #20
cj5huntingrig
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I had almost the same exact symptoms and can tell you my chain was stretched and worthless.
Also, please consider my earlier recommendation as I'm sure your mechanics did not check for a vacuum leak at the base of the intake manifold. Soak the intake down with carb cleaner where it connects to the head while running. It's an easy trick and if it hasn't been done yet, it needs to and will save you countless hours of scratching your head trying to figure out what the problem is. Let us know what you figure out.
Evan
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Unread 02-27-2013, 10:40 AM   #21
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Quote:
Originally Posted by 86cj74.2L View Post
I am surprised how many think you just screw in the compression tester and crank away. It must be held wide open throttle during cranking with all spark plugs removed.

What carb are you using?

When was your last tune up?
So tell me this. Why must ALL the plugs be out? Since it's not the actual psi that's important, but rather the difference in pressure between cylinders, would it really matter as long they were either all in or all out? Now if the concern is the actual comp. in a particular cylinder, I could see why. But then if that number is that crucial then an engine analyzer is probably the way you'd be testing it.
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Unread 02-27-2013, 11:01 AM   #22
86cj74.2L
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Pressure is as important as the difference between them. You may have valves that seal to 120psi and leak above that. Bla bla bla.

Some manufacturers spec a minimum cranking rpm for doing the check. Which requires a fully charged battery, as well as no spark plugs.

Some like Saturn will say XXX psi in so many revolutions. Which is easy count how many times the compression tester needle bumps Untill it stops increasing.

Doing a cold as well as a hot test is also good. If numbers are low cold and a few squirts of oil in the cylinder bring the numbers up its ring time. If no change with oil cold it could be the head.

Everyone does things their own way and think its the correct or best. The above is mine.
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Unread 02-27-2013, 11:49 AM   #23
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Quote:
Originally Posted by Matt1981CJ7
A stretched chain is about the only thing that would cause it to jump a tooth.

You can check for chain stretch, without removing the timing cover, by noting how many degrees the crank can be turned from TDC before the distributer rotor moves.

If you can rotate the crank more than 10 degrees before the rotor moves, your chain needs to be replaced. The procedure is spelled out well in the Haynes manual.

Good luck,

Matt
Thanks! I'll give that a try.
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Unread 02-27-2013, 11:50 AM   #24
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Quote:
Originally Posted by cj5huntingrig
I had almost the same exact symptoms and can tell you my chain was stretched and worthless.
Also, please consider my earlier recommendation as I'm sure your mechanics did not check for a vacuum leak at the base of the intake manifold. Soak the intake down with carb cleaner where it connects to the head while running. It's an easy trick and if it hasn't been done yet, it needs to and will save you countless hours of scratching your head trying to figure out what the problem is. Let us know what you figure out.
Evan
Yeah that's been done, and a smoke test as well. It is sounding more and more like the timing chain.
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Unread 02-27-2013, 12:37 PM   #25
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How many miles are on it?


What carb?
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Unread 02-27-2013, 12:55 PM   #26
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Quote:
Originally Posted by 86cj74.2L
How many miles are on it?

What carb?
Carter one barrel, remanufactured. I don't think it is the carb. Itnwas running worse before I replaced the carb. No idea how many miles.
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Unread 02-27-2013, 02:01 PM   #27
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Quote:
Originally Posted by ironbyron1 View Post
Yeah that's been done, and a smoke test as well. It is sounding more and more like the timing chain.
ok my 2cents!

I know you have tried the vac leak and i had a situation when i rebuilt my 258 and it was missing pretty good and i couldn't figure it out. i had someone here tell me to use propane, carb cleaner and etc. I did all that and couldn't figure it out. I did this probably ten times then on the 11 time did it again but just drenched it and sure enough had a leak on #1 intake port underneath i wasn't putting enough WD40 on there. Long story short fix my issues.

Now as far as compression goes unless i missed it somewhere you haven't acutally checked the compression yourself or had someone else do this? If you have 70psi all the way down this is not a timing issue. compression will be there whether or not your timing is correct. I think you need to back up and resolve that first before you go anywhere else.

I wish you luck i know it is frustrating.
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Unread 02-27-2013, 02:10 PM   #28
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master,

I think the consensus is the 70 compression readings are bogus. The shop is feeding the OP a pile....

Matt
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Unread 02-27-2013, 02:17 PM   #29
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master,

I think the consensus is the 70 compression readings are bogus. The shop is feeding the OP a pile....

Matt
right! sounds like he needs to go rent a compression tester and find out for sure huh? I know every mechanic I have ever talked to or known(my dad) for one starts there. You might have one that is 70psi but all of them? someone goofed just need to get better FIRST HAND readings.
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