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Guest Message by DevFuse

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How to compression test

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1 reply to this topic

#1 thedoctor


    USMB is life!

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  • Lancaster

Posted 26 January 2005 - 09:54 AM

I need tips on how to do a compression test correctly. I saw a tester at Sears with 14 mm thread for about $25. Is that a good tester or is there another kind I should get. Obviously this is the first time I've done this. Any tips, cautions? I have an 83 EA81 166 K, won't cold start, loosing coolant, sometimes seems like it's not running on all cylinders.

#2 thealleyboy


    Subaru Derelict

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Posted 26 January 2005 - 10:14 AM


That Sears guage should be fine.

First thing is to make sure your battery is at full stregnth. Next, you'll want to rig something up to ground the coil wire. Two alligator clips and a length of wire will work.

Run the motor to operating temp {if possible}. Remove all the plugs. Ground the coil wire. Thread the guage into the head, and make sure it is sealed, so no air escapes. Let the moter spin for approx 10 seconds for each cylinder.

There is no particular cylinder order in this procedure, but always take at least two readings to assure consistancy.

If you want opinions on what the readings mean, post your results here.

good luck, John

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