Compression testing can be done in several different ways.

1- READING PRESSURE FROM SPARK PLUGS: The spark plugs are removed and a pressure gauge 7 pressure gauge is connected and the starter is pressed. This process is repeated for all spark plugs and the differences are compared. It is not useful in new technology vehicles as spark plugs are difficult to access and remove.

2- CYLINDER COMPARISON WITH VOLTAGE / CURRENT: Cylinder comparison is made with oscilloscope. This method is done in several different ways. Method of voltage reading: If all cylinders are in good condition while cranking, each cylinder should decrease the battery voltage by an equal amount during cranking. If one or more cylinders are weak, the voltage drop of that cylinder will be small during cranking. Therefore, if the battery voltage is carefully read and recorded while cranking, weak cylinders can be detected. However, it cannot be determined how many cylinders are weak. Synchronous voltage reading method: In the voltage method, if a connection is made to the spark plug cable or one of the cables going to that cylinder to get a trigger signal, then both the cylinder comparison process is performed and how many numbered cylinders are weak is determined.