Here is how you run a Compression test. Itā€™s actualy quite simple, but a lot of people skip certain steps and end up getting wacky numbers. This thread is to ensure that no one here has this problem.
Running a compression test should ALWAYS be done before slapping a turbo onto a motor. As a wise man (Marty) once told me, boost projects will take the smallest issue you have, and put it center stage. You donā€™t want that one problem to be piston rings
Anyway, here we go.
Rent a compression tester from Autozone, should be like 40 bucks but you get it all back when you return it. This is what it looks like..
Assembly is very straight forward..
1- Take out your spark plugs (Remove all of them, and leave the holes open, the only one that should not be open when performing the test, is the one with the tester screwed in)
2- pull the ECU fuse so you dont get any fuel or spark to the motor.
3- Screw the tester into the number one cylinder
4- Put the accelerator all the way to the floor, and crank the motor for a few seconds.
5- Record the PSI reading for that cylinder
6- There should be a button somewhere on the tester to reset it, be sure to do this before moving on to the next cylinder.
Repeat steps 3-6 for each cylinder and compare your numbers. General rule of thumb is that they should all be within 10% of each other. Some will argue that its better to have them within 10psi of each other, but 10% seems pretty standard, at least from what I've read.
Good luck and have fun!
Another good test to run is the Leakdown Test. More Info here (Thanks RonJ and OP of this DIY): http://www.carcraft.com/techarticles...ter/index.html