compression question -
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back > Models > Jeep Wrangler Forums > YJ Wrangler Technical Forum > compression question

End of Summer Sale, 20% OFF!2007 - 2011 Jeep JK Long Arm Lift KitsIntroducing MONSTALINER™ UV Permanent DIY Roll On Bed Line

Unread 10-08-2002, 03:30 PM   #1
Registered User
Join Date: Jul 2002
Location: Montreal, Canada
Posts: 52
compression question


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

DanyJeep is offline   Reply With Quote
Unread 10-08-2002, 03:57 PM   #2
JF Administrator, eh?
NaeKid's Avatar
1988 YJ Wrangler 
Join Date: Nov 2000
Location: Calgary, AB
Posts: 6,880
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
Hello, my name is Vance and I am a Jeepaholic.
Its better to be naked with your friends, than to be clothed with your enemies
  • From street to trail, '88 YJ on 38" tires does it all well
  • Silver 2006 TJ Unlimited, zombie ready as the daily-driver
  • a Kawasaki KLR650 DualSport bike

- - - - - - -TEOTWAWKI- - - - - - -

NaeKid is offline   Reply With Quote
Unread 10-10-2002, 11:47 AM   #3
Registered User
Join Date: Jul 2002
Location: Montreal, Canada
Posts: 52
nae kid.....

would you be able to confirm those numbers?
please. i'll tell you why later
DanyJeep is offline   Reply With Quote
Unread 10-10-2002, 12:03 PM   #4
Registered User
2005 LJ Wrangler 
Join Date: Jan 2002
Location: Oxford, CT
Posts: 2,435
From the Haynes manual: Cylinder compression pressure should be between 155 to 185 psi.
2005 LJ Impact Orange 4.0L Automatic (Tigger) - new ride
1991 YJ Sahara 4.0L Automatic
1978 Dodge Lil Red Express - work in progress
RCHavok797 is offline   Reply With Quote
Unread 10-10-2002, 12:57 PM   #5
Registered User
Join Date: Apr 2001
Location: Republic of Newfoundland
Posts: 123
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.
No officer, that wasn't an accident. I did that on purpose...
Newfie is offline   Reply With Quote
Thread Tools

Suggested Threads

Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. is not in any way associated with Jeep or the Chrysler Corp.