2nd Generation Specific 1986-1992 Discussion

How to use a compression tester

Old 11-20-2006, 12:26 PM
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I just bought one of these, and have a couple questions.



1. Isn't there a way to disable the mechanism that makes the needle hold at it's highest position?



2. This thing has a "quick connect", the same type as on my hose that I use for my air compressor. If I connect this hose to it, so I could sit in the driver seat with one hand on the ignition, and the other holding the gauge, will the added length of the hose skew the reading?
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Old 11-20-2006, 02:21 PM
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1. yes, you can remove it, or maybe hold it down?



2. it might drop the readings, but not enough to matter, and b) you're not looking for the actual number, but more key is 3 even bounces. the compression guages vary with temp, age, humidity, etc etc
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Old 11-20-2006, 02:31 PM
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you dont have to remove the schrader valve..

just hold it down to view the pulses..
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Old 11-20-2006, 02:58 PM
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Okey dokey, thanks for the info!
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Old 11-21-2006, 05:48 AM
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Originally Posted by j9fd3s' post='846073' date='Nov 20 2006, 03:21 PM

1. yes, you can remove it, or maybe hold it down?



2. it might drop the readings, but not enough to matter, and b) you're not looking for the actual number, but more key is 3 even bounces. the compression guages vary with temp, age, humidity, etc etc


So your actually looking for the needle to bounce 3 times? Whats this indicate?
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Old 11-21-2006, 06:46 AM
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also where do you actually connect the tester?
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Old 11-21-2006, 07:36 AM
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You remove a spark plug, and it threads into the spark plug hole. You disable the fuel (and spark? I'm not sure), and crank the starter. The needle bounces as the combustion chamber compresses each time.



3 even bounces would indicate compression on all 3 sides of the rotor. If there were 1 big bounce and 2 very small ones, this would indicate a busted apex seal.
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Old 11-21-2006, 07:49 AM
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how do you disable the fuel?? never had to do any of this but theres no time to learn like the present.
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Old 11-21-2006, 09:50 AM
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Originally Posted by Baldy' post='846157' date='Nov 21 2006, 05:36 AM

You remove a spark plug, and it threads into the spark plug hole. You disable the fuel (and spark? I'm not sure), and crank the starter. The needle bounces as the combustion chamber compresses each time.



3 even bounces would indicate compression on all 3 sides of the rotor. If there were 1 big bounce and 2 very small ones, this would indicate a busted apex seal.


exactly!
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Old 11-21-2006, 12:58 PM
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Originally Posted by ExplicitRotary' post='846161' date='Nov 21 2006, 05:49 AM

how do you disable the fuel?? never had to do any of this but theres no time to learn like the present.
Unplug the fuel pump and crank it over a few times to get rid of any fuel left in the delivery system.



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