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Old 12-26-2010, 09:48 PM
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compression test

I bought a comp. tester never used one do I screw it to the #1 cylinder hole and turn motor over with a trigger switch and watch it for the highest peak or do it another way?

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Old 12-26-2010, 10:18 PM
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Remove all your sparkplugs, disconnect the coil wire and use either the key ignition or remote trigger. Do each hole, screw in the tester, hold the throttle wide open and crank 3 to 5 revolutions, or until it stops increasing, you'll hear each time that cylinder cycles.

You should do a dry and wet test. The wet being a few shots of motor oil in the cylinder before the crank. Compare the dry and wet readings, if there's a significant difference, you have weak or damaged rings. If no real difference and you're experiencing motor problems, it points to the valve train (if readings are low).
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Old 12-26-2010, 10:19 PM
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Remove all the spark plugs, hold or wire the carb wide open, disable the spark(either disconnect hot wire to distributor or coil), and then screw in compression gauge. Spin the motor over with the starter so that it makes at least 3 "pumps" at the cylinder you are checking, and either do them all at 3 pumps or go more than 3 until the guage tops out - either/or, but do all cylinders the same so readings are all done with the same method.

Last edited by ericnova72; 12-26-2010 at 10:20 PM. Reason: same basic answer as above post
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Old 12-26-2010, 10:20 PM
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Originally Posted by sadie00
I bought a comp. tester never used one do I screw it to the #1 cylinder hole and turn motor over with a trigger switch and watch it for the highest peak or do it another way?
Begin with a freshly charged battery and known-good cables.
Remove all spark plugs to make the motor easier to turn over. Disable the coil (disconnect + wire).
Wire the throttle blades wide open on the carb or throttle body to allow the motor to breathe.
Screw the tester probe into the spark plug hole.
Press the button and let the pressure build through 4 or 5 cycles. You'll see the needle come up every time you go through a cycle. When the needle fails to climb any higher, take the reading and write it down. Move to the next cylinder and repeat.

Sorry 68NovaSS and Eric, you were posting as I was typing.
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Old 12-27-2010, 08:04 AM
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compression test...

Hi,if you have low compression on 2 adjacent (side by side) cylinders,thats a sign of a blown head gasket,do test as stated in previous posts.
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