Well, I think I found my engine problem *Update* - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 02-10-2004, 11:43 PM Thread Starter
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Well, I think I found my engine problem *Update*

A little background. A week and a half ago, I drove my jeep on the freeway for about 40 minutes at 65-70 mph. That puts the engine (AMC 360) around 3000=3100 rpm. Getting to the end of the off ramp, the engine barely wanted to idle. Tonight I finally got the time and warm enough weather to do a compression check. Here are the results.

#1: 152
#2: 137
#3: 145
#4: 160
#5: 150
#6: 145
#7: 142
#8: 20

The #8 spark plug was velvety black so there was fuel being burned and no water present. I removed the valve cover and saw the valves opening and closing like they should. There is no blowby from the crank case so the piston and rings are fine. That leaves only one possibility. I have a burnt exhaust valve. Hopefully it will warm up enough soon to take care of it. [img]images/graemlins/crybaby.gif[/img]
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post #2 of (permalink) Old 02-11-2004, 12:08 AM
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Re: Well, I think I found my engine problem

1. Did you do a Wet/Dry compression test?
2. I'd agree that it seems like a burned valve,
3. Sometimes you can hear the compression leaking in[*]Intake manifold[*]Exhaust Manifold.
4. If you do the compression by hand.
5. Bummer..but,
6. I'm wondering how the one valve can cause,
7. The engine to attempt to die...at lower RPM?
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post #3 of (permalink) Old 02-11-2004, 02:01 AM
 
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Re: Well, I think I found my engine problem

Hey Will,
I was reading your other post and you mentioned the MSD....You may want to check the connectors that attach the wire from the MSD to the Solenoid and the one going to ground ...Mine ( although used when I bought it) had those combo crimp/ solder connectors but they were never soldered...SO they started pulling apart causing the jeep to stall while driving it and rejump itself if I left it in gear.
When the plastic insulator heated up it allowed the wire and connector to break contact , as it cooled it pulled them back together allowin it to start or rejump itself while moving.
Kinda freaked me out driving at 50 MPH and have the jeep stall out, then keep coasting to get off the road and it self starts.

AS far as your tach problem ...my shop tach works off the TFI coil connection, For setting the timing . I do not have a tach in the jeep.
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post #4 of (permalink) Old 02-19-2004, 10:12 PM Thread Starter
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Update on engine

Well, I got the head off and found some good news. Turns out the exhaust valve isn't burned. The exhaust valve spring broke but it wasn't very easy to notice where it was before I removed the head. The valves both look fine, just need to wire wheel the exhaust vavle and reinstall it. Should be able to get it back together tomorrow night.
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post #5 of (permalink) Old 02-19-2004, 11:37 PM
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Re: Well, I think I found my engine problem *Update*

Hopefully that gets it Will. Sucks that you tore it apart, BUT....a whole lot cheaper than having to go all the way through the head.
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post #6 of (permalink) Old 02-20-2004, 12:42 AM Thread Starter
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Re: Well, I think I found my engine problem *Update*

I am fortunate that my dad had a valve grinder and valve seat ginder but that would be a lot of work. Also fortunate that the exhaust valve isn't deformed, just carboned up a little. The sealing surfaces are still intact. Shine them up with a wire wheel and it will be ready to go. When I rebuilt the engine a few years ago, my dad did one head to teach me how and I did the other head.
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post #7 of (permalink) Old 02-20-2004, 01:46 AM
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Re: Well, I think I found my engine problem *Update*

that sounds almost exactly what happened to mine I have an AMC 401 it ran like crap and the plastic diverter valve melted too. I replaced that with a new one and it still ran bad. when I step on the gas it bogs out unless I do it real slow. I dont know too much about engine repair just mostly what everything is where it is and what it does. is it dificult to fix?
post #8 of (permalink) Old 02-20-2004, 08:30 AM Thread Starter
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Re: Well, I think I found my engine problem *Update*

It's not hard to fix, it took me about 3 hours last night to pull the head off. Do a compression test first though. If all your cylinders are around 140-160 psi, that is not your problem.
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post #9 of (permalink) Old 02-20-2004, 08:39 AM
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Re: Well, I think I found my engine problem *Update*

is it just coinsedence, or is it some sort of design issue w/ AMC V8 that #8 is the one with the constant problems. seems everytime i hear about a cylinder issue it's always #8.. same with mine too. [img]images/graemlins/confused.gif[/img]
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post #10 of (permalink) Old 02-20-2004, 08:53 AM
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Re: Well, I think I found my engine problem *Update*

1. It's not a fluke.
2. I'm sure CJDave could describe it better,
3. But some cylinders on a V8 - or I6,
4. "Work" harder than others...
5. And when a problem crops up,
6. It's usually associated with these cylinders.
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