You can rent a compression tester from most auto parts stores like auto zone. The way to do a compression test correctly is to run the motor a bit let it get up to normal running temp. then pull all the plug from each cylinder. The hook the compression tester into a one cylinder at a time with all pugs out, crank the motor over say 6 to 8 revolutions and read the compression gauge let it sit a couple minutes see if it holds the pressure. then move on to the next cylinder till all have been done.