Compression check (Peugeot J5)

Compression testing is performed to ensure that valves close properly, piston rings are intact, and there are no other defects in the cylinders. In this case, the engine must be warmed up to its operating temperature.

• Remove the spark plugs.
• Open the throttle and air valves.
• Insert a pressure gauge into the hole under the first spark plug to measure compression.
• The assistant should press the gas pedal all the way down and turn on the starter.
• Turn the engine until the arrow reaches its maximum position.
• In the same way, check all cylinders sequentially.

It is generally accepted that no cylinder should have compression lower than 80% of the best cylinder's compression.

Low and uneven compression is usually caused by worn piston rings.