How to do a compression test?

[saturnthegiant]

Wondered if anyone could tell me the steps to do a compression test on a '99 Jimmy? With a screw in type gauge.... do you have to disable the fuel pump, etc. I need to determine if the head gasket is blown. Thanks.

[goser]

http://www.automotiveforums.com/vbul...d.php?t=954856

[tempfixit]

Originally Posted by saturnthegiant

Wondered if anyone could tell me the steps to do a compression test on a '99 Jimmy? With a screw in type gauge.... do you have to disable the fuel pump, etc. I need to determine if the head gasket is blown. Thanks.

Here is a video that shows a quick way to test for blown head gasket wih a compressor.

http://realfixesrealfast.com/realfix...nder_Head.html

[old_master]

What are the symptoms that you're experiencing? Keep in mind that the 4.3L engine has very few head gasket failures. Most of the time when they are replaced, it's due to a misdiagnosis. Lower intake manifold gaskets are a very common failure.

Remove all of the spark plugs, prop the throttle open, install the gauge and crank the engine over until you hear/feel 4 compression strokes. Do this for each cylinder and write down the results and label them as "dry". The test results should not vary more than 10% from the highest to lowest cylinder. Then squirt about a tablespoon of oil in each spark plug hole and check compression again on all cylinders labeling this test "wet". The wet results will be higher, but should not vary more than 10% from highest to lowest cylinder. The wet test helps the rings seal and if the compression spikes higher on a particular cylinder, one or both compression rings are cracked/broken.

[saturnthegiant]

Well, turns out the head gasket is blown, as i suspected. I'm having it repaired as we speak. Thanks for the help, guys!

[phillipshaw]

Ive been expereincing it too. and it was so difficult for me to fix it, that's is why I ask some help to experts.