Engine compression specifications are checked with either a manual compression gauge or an electronic engine analyzer. The manual method is more practical for those who want to complete the compression check themselves.
A manual check begins by removing the fuel pump and fuel-injection fuses. Warm up the engine as a cold engine can alter test results. Next, disable the ignition coil then put the compression tester into one cylinder spark plug hole. Hold the throttle open to allow for air intake, then rev the engine for 10 full revolutions. Check and document the level on the compression meter. Repeat the full process for all cylinders.
Engines in good condition should have a reading of 100 psi per cylinder. All the readings should be within 10 percent of each other for compression to be considered acceptable.
Low compression in all the cylinders could mean the engine tends to flood and the excess fuel has washed all the oil off the cylinder walls. Low pressure readings could also indicate a timing problem within the engine. If the low reading is only in one cylinder, internal engine damage could exist. High compression could reveal carbon build up that requires a high pressure de-carbonization of the engine.