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Unread 02-26-2013, 07:52 PM   #1
ironbyron1
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Compression question on 258

I've been told by one mechanic my 258's compression tested at 150. Another shop told me today it is 70 in all 6 cylinders. 150 is spec. Would it even run at 70? And the shop that told me 70 said it is the rings not the valves. If the rings were that bad wouldn't it smoke like the dickens? It doesn't smoke one bit.
The reason for the test is trying to find why it is so hard to start, and misses so much. That aside, it is running better and more powerful than ever. I still wonder if it has jumped a tooth on the timing, or maybe the timing chain is worn. It won't harldy run at all if you set the timing properly. It has to be advanced a lot to run. Any advice please! Oh and it has new, carb, distr, control module, dstr cap, rotor button, plugs and wires, fuel pump, vacuum is fine, fuel filter is fine.

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Unread 02-26-2013, 08:19 PM   #2
86cj74.2L
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Buy a tester and do it yourself. They are not expensive. Or rent from a autoparts store.
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Unread 02-26-2013, 09:09 PM   #3
cj5huntingrig
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Originally Posted by 86cj74.2L View Post
Buy a tester and do it yourself. They are not expensive. Or rent from a autoparts store.
X2. I bet you have a leak at your intake manifold. Soak the intake with carb cleaner where it connects to the head while running (cold) and if it picks up speed or smooths out, you need to replace your gasket.

Also, to answer your question, the guy who told you 70 is probably lying.
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Unread 02-27-2013, 01:44 AM   #4
ironbyron1
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X2. I bet you have a leak at your intake manifold. Soak the intake with carb cleaner where it connects to the head while running (cold) and if it picks up speed or smooths out, you need to replace your gasket.

Also, to answer your question, the guy who told you 70 is probably lying.
No intake leaks have been found either. They could be lying, but I think the guy who did the test just didn't know what he was doing. Either way I don't see how he can be right.

Thanks for your advice.
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Unread 02-27-2013, 03:16 AM   #5
86cj74.2L
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Quote:
Originally Posted by ironbyron1

No intake leaks have been found either. They could be lying, but I think the guy who did the test just didn't know what he was doing. Either way I don't see how he can be right.

Thanks for your advice.
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?
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Unread 02-27-2013, 05:32 AM   #6
BagusJeep
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SOunds indeed that the carb was not held open.
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Unread 02-27-2013, 05:34 AM   #7
ironbyron1
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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?
All of the things that I listed as having been done are a work in progress to get it back up and running. It died on me one day and wouldn't run at all. From there all the things I listed have been done, starting with 3 control modules. The guy who put the first one one decided it should have a detachable pigtail on it so he wired one in. Well he wired it backwards and when it wouldn't run he blamed it on the carb. Turns out he hates carbs and will not touch one. The next guy who worked on it discovered that, guess what, the control module the first guy put in was burned up. So he put a new one in, only to have it promptly burn up since the pigtail was still wired backwards. So, he figured that out and now the engine is running again, but just barely. Keep in mind it was running fairly good before it died on me. Then all the other stuff listed above was added in an attempt to bring it back around.
The only thing that hasn't been checked is the timing chain, and the valves/pushrods have not been closely scrutinized. That was supposed to have been done yesterday, but when they found the compression to be 70 (I still think that has to be wrong) they went no further.
Thanks!
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Unread 02-27-2013, 05:58 AM   #8
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It sounds like you still need to find a competent mechanic, or learn how to work on your CJ yourself.

I doubt an engine with 70 compression would even run. If it did, it would smoke like Cheech and Chong's van on a Saturday night. I can't believe your mechanic is trying to sell you that crap. Aren't there ANY honest wrench-monkeys any more?

Have you, or your mechanic even checked timing? I think your instincts are right on the money. Timing chains often stretch, and can skip a tooth.

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Unread 02-27-2013, 06:31 AM   #9
ironbyron1
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Originally Posted by Matt1981CJ7 View Post
It sounds like you still need to find a competent mechanic, or learn how to work on your CJ yourself.

I doubt an engine with 70 compression would even run. If it did, it would smoke like Cheech and Chong's van on a Saturday night. I can't believe your mechanic is trying to sell you that crap. Aren't there ANY honest wrench-monkeys any more?

Have you, or your mechanic even checked timing? I think your instincts are right on the money. Timing chains often stretch, and can skip a tooth.

Matt
I do as much work as I feel I can handle. I agree, at 70 I don't think it would run and would smoke like Mount St Helens! I'm having someone give me a third opinion on the compression soon, hopefully today.
As for the timing. I think it jumped time when the first guy who botched the control module, kept cranking it trying to get it to run right with the module hooked up backwards.
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Unread 02-27-2013, 06:42 AM   #10
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So timing has never been checked thru-out this whole ordeal? Really? I'd be hauling my CJ out of that shop ASAP. They sound like a bunch of clowns.

If you can turn a wrench, and read a repair manual, you can do about 95% of all repairs on a CJ, yourself. Just sayin'....

I know wrenching isn't for everyone, but I hate being at the mercy of untrustworthy mechanics, so I forced myself to learn how.

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Unread 02-27-2013, 06:51 AM   #11
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I couldn't agree more Matt. I embody that statement
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Unread 02-27-2013, 07:00 AM   #12
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Vinny,

You were in the back of my mind when I wrote that.

Your situation flat pisses me off. I can only imagine how you feel...

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Unread 02-27-2013, 07:02 AM   #13
ironbyron1
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Timing has been checked but has to be advanced a LOT for it to run. I've thought for the longest time that it has jumped a tooth. It could be as simple as a stretched chain I suppose.
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Unread 02-27-2013, 07:04 AM   #14
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Everyone seems to jump straight to the "it wouldn't run if it had jumped time thing". I tend to agree, but maybe it would run if it only jumped one tooth and you advanced the timing!
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Unread 02-27-2013, 07:12 AM   #15
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Yes, you can advance, or retard, timing to make an engine run after it has jumped a tooth, but it won't run well.

There are several examples of this documented in threads, here.

How far advanced did they set it to get it to run? And why in he!! didn't that raise concerns about the timing chain with those clowns? Ugh....

Matt
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