2nd Generation Specific 1986-1992 Discussion

Compression Check

Old 01-12-2004, 12:50 PM
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I remember reading here that there is more to doing a compression check than just removing a plug and hooking up a gauge. I know the EGI fuse and battery cables should be removed so it doesn't fire but is there anything else?



I tried a search but it comes up with too much crap to wade through for such a simple question.



Thanks.



Greg
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Old 01-12-2004, 01:12 PM
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Fully open throttle while testing. Your not gonna get a very acurate reading with a regular comp tester.
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Old 01-12-2004, 01:19 PM
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i pulled the egi relay and the fuel pump fuse under the dash, disconnected the wires from the plugs (extra), the battery cables i left hooked up to power the starter. remove only the leading (lower) plugs, install gauge and disable gauge's schraeder valve or keep relief button depressed so that needle bounces as each rotor tip swings by. crank engine and watch for consistent bounces around 90...don't crank for more than 10 seconds and let starter rest after cranking.



but yeah, this isn't the most accurate...just give you an idea of your compression



good luck,



fritz
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Old 01-12-2004, 01:29 PM
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fsm gives the best method to be accurate as possible,,, it's kinda hard to describe all the math involved... (well for me it is...)
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Old 01-12-2004, 01:41 PM
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First of all... this is how bad of a day I have been having to suggest disconnecting the battery cables...What the **** was I going to do...hand crank the E-shaft from the pulley



Thanks for the help guys...I am only looking to get an idea of what is happening not to get anything absolutely accurate.



Thanks



Greg
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Old 01-12-2004, 01:47 PM
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oh, and make sure your battery is fully charged and your engine isn't flooded
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Old 01-12-2004, 02:00 PM
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Originally Posted by gazellis' date='Jan 12 2004, 11:41 AM
What the **** was I going to do...hand crank the E-shaft from the pulley
Now thats something to see.
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Old 01-13-2004, 07:35 AM
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Originally Posted by RONIN FC' date='Jan 12 2004, 11:12 AM
Your not gonna get a very acurate reading with a regular comp tester.
I concur doctor!



However, Gazellis, there is something you can learn from a normal compression checker. When you are cranking, 2 high compression needle bounces followed by one low needle bounce means one bad apex seal!



No real peak bounces at all means bad side seal(s).



I hate referring to a haynes manual over the FSm but check out the haynes engine section and it goes into this a little.



If you do not have a haynes manual I will check for you when I get home tonight



Good luck
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Old 01-13-2004, 08:01 AM
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I have a Haynes manual. I will look at it when I get home today. Thanks for the good information though.



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Old 01-13-2004, 08:39 AM
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Originally Posted by twstdmtl' date='Jan 13 2004, 05:35 AM
I concur doctor!



However, Gazellis, there is something you can learn from a normal compression checker. When you are cranking, 2 high compression needle bounces followed by one low needle bounce means one bad apex seal!



No real peak bounces at all means bad side seal(s).



I hate referring to a haynes manual over the FSm but check out the haynes engine section and it goes into this a little.



If you do not have a haynes manual I will check for you when I get home tonight



Good luck
1 seal, seals 2 faces. So if 1 is broken, he should get 2 low bounces.
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