Compression test question
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Compression test question
2008 Mercury Mountaineer 4.0 SOHC
I've been trying to track down an intermittent #2 cylinder misfire. Wont bother with all those details because this question is only about the compression test.
I've tested it several times now and It averages 155. I always pull the wire to the coil and turn the engine over several times to get my reading. Today I forgot to pull the coil wire and it started up. No big deal turned it off pulled the wire and checked the gauge. It read 50 lbs did it again with no spark and 155. I repeated the test with engine started and 50lbs, 155 when just turning over. IS THIS NORMAL? what caused the low reading? To high of RPM?
I've been trying to track down an intermittent #2 cylinder misfire. Wont bother with all those details because this question is only about the compression test.
I've tested it several times now and It averages 155. I always pull the wire to the coil and turn the engine over several times to get my reading. Today I forgot to pull the coil wire and it started up. No big deal turned it off pulled the wire and checked the gauge. It read 50 lbs did it again with no spark and 155. I repeated the test with engine started and 50lbs, 155 when just turning over. IS THIS NORMAL? what caused the low reading? To high of RPM?
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Joined: Sep 2017
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50 maybe low, read this article interesting way to do compression test's
https://support.alldata.com/article/...pression-tests
https://support.alldata.com/article/...pression-tests
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Joined: Jun 2012
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well thats what I thought but I'm not sure where to go next! That was the first thing I did to eliminate a mechanical problems. Pressure checked out fine so I moved on. These new readings could also be my gauge it's at least 40 years old. It was a hand me down from my Dad and he probably bought it used. I might breakdown and by one or just take it to a pro and have them test/evaluate the problem. Will be good to let someone else think about it.
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