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Compression Readings
Topic Started: Jan 11 2013, 11:21 AM (544 Views)
gianas
Member
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Galen, when you've got that figured out, please tell me how you do the compression check. The instructions I've been given conflict, and I don't want to do it incorrectly, inaccurately.

Any other instructions on doing a compression check the right way would help. For example, is adjusting the carb choke always involved, as one set of instructions say?

Also, what NOT to do would help knowing ... and why.
Thanks,

greg
Greg Gianas
Redmond, Washington
1954 3B, daily driver; old, beat up but still strong,
last vehicle I'll probably ever own,
purchased May 2012;

first vehicle and jeep owned: back in 1965-66 (1965 CJ-5, Hurricane 134 engine); no better memories
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Galen
Member
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Greg,

The compression tester I have has the screw in fitting to the spark plug hole and to the gauge. First off remove the center coil wire so as not to start the jeep when cranking motor. I simply attach the compression tester one at a time to each spark plug hole, crank the motor until the needle stops rising (5-10 seconds). Using the button on the gauge, reset after each cylinder. Then compare reading and they should be w/in 10% of each other. The number itself is less important than the differences between the four cylinders. There is no role in the carburetor in this test. You are determining the piston ring condition. The motor is NOT running during the test. I am no expert but this is what i know. Anyone else jump in.
1954 CJ3B -Transport Yellow-
1953 B4 Dodge Power Wagon
1941 Dodge WC 1/2 ton military
1967 Plymouth Valiant
Culpeper, VA
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Galen
Member
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I ran a compression test on my engine and all four came in between 110-115# psi. How does this align with specification?
1954 CJ3B -Transport Yellow-
1953 B4 Dodge Power Wagon
1941 Dodge WC 1/2 ton military
1967 Plymouth Valiant
Culpeper, VA
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Galen
Member
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Forgot to mention if the compression is low its an indication of leaky- bad valves also
1954 CJ3B -Transport Yellow-
1953 B4 Dodge Power Wagon
1941 Dodge WC 1/2 ton military
1967 Plymouth Valiant
Culpeper, VA
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oldtime
Member Avatar
MODERATOR
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Kinda low is a bad sign but very uniform is a good sign.
Were these readings taken according to W/O instructions ?
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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Galen
Member
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No, I am not aware of W/O instructions-can you forward. The readings may have been higher but I had to run from the seat to the engine compartment all the while the gauge was slowing dropping- not the best instrument. I may not have cranked the motor long enough.
1954 CJ3B -Transport Yellow-
1953 B4 Dodge Power Wagon
1941 Dodge WC 1/2 ton military
1967 Plymouth Valiant
Culpeper, VA
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oldtime
Member Avatar
MODERATOR
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Can someone scan and upload compression testing instructions found in one of the universal service manuals (USM's)...........
Currently building my final F-134 powered 3B .
Rock Crawler using factory parts from the Willys Motors era (1953-1963)

http://s4.zetaboards.com/CJ3B_Bulletin_Board/topic/30228766/1/#new
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Rus Curtis
Member
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Here's a copy from my SM

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Rus Curtis
Alabama
'54 CJ-3B "Green Gruntt"
Bantam T3-C
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