Compression/ buring oil
Thread Starter
Member
Joined: Sep 2011
Posts: 117
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From: oregon
Year: 1993
Model: Cherokee
Engine: 4.0
Compression/ buring oil
1993 Inline 6 auto 124,000 miles. Burning oil did a comresion test front and back cylinder were 130psi all the others were 135psi verying 1-2 psi. the front cycilinder took alot of time to get the pressure had to turn it over way more than the others. valves or valve guides why im buring oil? Also my spark plugs were pretty bad so any certain brand that is good? thanks
Caracticus Potts The Mod
Joined: Jul 2009
Posts: 5,298
Likes: 9
From: Hainsville, NJ
Model: Grand Cherokee
Do the test over again, the test is only good for diagnosis when you "puff" each cylinder with the same number of revolutions, but it sounds like you may have a burned valve.
CF Veteran
Joined: Apr 2009
Posts: 18,786
Likes: 14
From: CT.
Year: 88
Model: Comanche (MJ)
Engine: 4.0 HO
Champion coppers work really good and X2 with ****** on same ratio. One or 2 turns should be more accurate.
Also do a leak down by compressing air into each cylinder each one on compression stroke. Then you will be able to hear in any air is rushing out of the intake or exhaust.
Also do a leak down by compressing air into each cylinder each one on compression stroke. Then you will be able to hear in any air is rushing out of the intake or exhaust.
Senior Member
Joined: Aug 2011
Posts: 760
Likes: 6
From: Landers, CA
Year: Several
Model: Cherokee
Engine: 4.0
If the plugs were really bad, put in the new ones and drive it 100 miles, test again.
Bad plugs can make you think there's a compression problem when there isn't.
To get significant readings:
ALL PLUGS OUT
THROTTLE BLOCKED OPEN
SAME NUMBER OF PULSES EACH CYLINDER
If one is LO - shoot 3 squirts of engine oil in the hole, rotate engine 3 times to spread the oil, test again
if comes up to normal, rings, if not, valves.
do a leak down test before panicking.
Bad plugs can make you think there's a compression problem when there isn't.
To get significant readings:
ALL PLUGS OUT
THROTTLE BLOCKED OPEN
SAME NUMBER OF PULSES EACH CYLINDER
If one is LO - shoot 3 squirts of engine oil in the hole, rotate engine 3 times to spread the oil, test again
if comes up to normal, rings, if not, valves.
do a leak down test before panicking.
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