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Unread 12-13-2011, 07:54 PM   #1
mangoman123
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1990 YJ Wrangler 
 
Join Date: Oct 2011
Location: Niceville, Fl
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1990 yj compression test results need help

OK today I did a compression test. My results were
Cylinders 1 2 5 160 Psi
Cylinders 3 4 6 150 psi
Is this good or bad? Should I have the ten pound difference between them?

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Unread 12-13-2011, 07:56 PM   #2
mangoman123
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Oh, its the 4.2l engine. Sorry
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Unread 12-13-2011, 10:10 PM   #3
ratmonkey
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Its perfect.
Anything under 120 psi is getting worn, around 120psi average with a 15psi spread you should figure out which end of the cylinder needs refreshed(head/valve job or rings)
One super low cylinder is usually a head gasket (if no racket from the valve train or a busted piston is expected)
under 100psi average the motor needs rebuilt in full
Under 80psi it probably wont run.
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'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.

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Unread 12-14-2011, 09:31 AM   #4
oteps
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Yep those results are good. Are you having an engine problem or did you just want to check compression?
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Unread 12-14-2011, 03:40 PM   #5
mangoman123
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Weird feeling with power demand, like up hills, plus a knocking sound. This thing is killing me on new parts though.
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