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Old 06-14-2011, 01:46 PM
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Compression test tips

Fixing to do a compression test on a 6.0 Ls, I realize its a pretty straight forward
procedure but, would like to hear some tips/procedures ya guys use......

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Old 06-14-2011, 01:57 PM
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Never have done a computer motor. Don't know about how to disable the ignition system like you would on a carb motor or even if you have to at all. Someone else will probably join in here, but this is how I do a carb motor....
Bring the motor up to operating temp so that all the parts are the proper dimension.
Remove all spark plugs so the motor can turn easily.
Disable the ignition system so you don't start a fire.
Wire the carb throttle blades wide open so the motor can breathe.
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Old 06-14-2011, 02:27 PM
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What TechInspector says, plus if it's injected, relieve the pressure in the fuel line and pull the breaker / relay for the fuel pump so you are not injecting fuel into the manifold while cranking the motor.

I install the pressure tester into the cylinder and crank the engine through the compression stroke 6 times and then stop cranking and take a reading. If you find a cylinder that is significantly lower then the others (say 20% or more from the average of the others), you will want to do a leak down test to better determine where the issue is.
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Old 06-14-2011, 03:02 PM
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A leak down test at TDC is more valuable information then a compression test!!!
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