How Do You Do a Compression Test?

How Do You Do a Compression Test?

To perform a compression test, remove a spark plug, and take a reading using a compression tester kit. You need a spark plug socket and a compression tester kit.

  1. Consult the repair manual

    Consult the repair manual for your specific vehicle, and make adjustments accordingly.

  2. Warm up the engine

    Warm up the engine, and then turn it off.

  3. Disable the ignition system

    To disconnect the engine control unit, disconnect the wire from terminal 15, or unplug the coil packs to disable the ignition system.

  4. Insert a spark plug adapter

    Remove one spark plug. Read the tester kit's instructions to determine which adapter to use. Install the adapter in place of the spark plug.

  5. Attach a rubber hose to the adapter

    Attach the fitting on the rubber hose to the adapter. Twist the hose by hand to screw it into place.

  6. Insert the hose into the dial gauge

    Pull back the metal collar on the dial gauge, and insert the opposite end of the hose into the gauge's fitting. Slide the collar over the hose's fitting.

  7. Turn the key, and record the reading

    Insert the key into the ignition. Turn the key, and hold it for 10 seconds. Write down the reading.

  8. Release compressed air

    Press the button on the side of the gauge's fitting to release the compressed air.

  9. Remove the tester kit

    Uninstall the tester kit, and reinstall the spark plug.

  10. Repeat the test, and consult the repair manual

    Repeat the test with the remaining cylinders. Consult your repair manual to determine where the readings stand for your vehicle.