Remove all spark plugs, and pull the fuse on the fuel pump. There are two parts to the compression test, wet and dry. Start with the dry test. hook up the compression gauge, one cylinder at a time. With it hooked up, have someone crank the engine for 3-5 seconds. Record the highest reading. Many gauges will have a second needle that automatically sits at the highest reading. Make sure you reset that before the next test. Once you have recorded the value for each cylinder, move to the wet test. Exact same procedure, except you pour a small amount of oil into the cylinder just before you test it. About a tablespoon (someone correct me if that is the different amount that you use...) Basically you want oil around the piston rings. Again record the highest value of each cylinder.
The exact readings isn't that relevant. What you are looking for is consistency across the readings. You'll probably get around 110-150. If you get some cylinders with low numbers compared to the rest of the cylinders during the dry, then there is an issue with that cylinder. If the compression for that cylinder is still low during the wet test, then the problem is likely with a valve guide or gasket. If the cylinder compression increases during the wet test, then likely you have worn rings.
Edit: agree with Blooze...disconnect ICM as well...
[This message has been edited by Neils88 (edited 07-18-2014).]
