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Unread 10-08-2002, 04:30 PM   #1
DanyJeep
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compression question

hi,

I'd like to know what the compression should be at on a 94 yj 4cylinder mpfi
to my knowledge the compression ratio is 9.2 to 1
and i did a compression test and i got
130, 130, 135, 145,
is this a good compression?

thanx dany

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Unread 10-08-2002, 04:57 PM   #2
NaeKid
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Some of those numbers are a little low .. they should all be around the 145 to 155 mark (if I remember the numbers correctly). If you have a Haynes manual handy, the compression numbers should be listed in the 4-Cyl statistics page.

I am at work, so I can only go by what I think I remember reading while I was in the ThroneRoom
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Unread 10-10-2002, 12:47 PM   #3
DanyJeep
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nae kid.....

would you be able to confirm those numbers?
please. i'll tell you why later
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Unread 10-10-2002, 01:03 PM   #4
RCHavok797
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From the Haynes manual: Cylinder compression pressure should be between 155 to 185 psi.
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Unread 10-10-2002, 01:57 PM   #5
Newfie
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As long as all the cylinders are resonably close, you shouldn't have any issues. An older motor will not have anywhere near the compression that it came from the factory with. It's when you get 1 or two cylinders that are way out from the others that you need to worry. Your's are not completely unreasonable, but my guess is that it's almost time for new rings.
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