GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1998 🢒 Metro 🢒 Engine 🢒 Engine Electrical 🢒 Engine Compression Test

Perform a compression test in order to determine the cylinder compression pressure. Use a compression test in order to diagnose lack of power, excessive oil consumption, or poor fuel economy.

  1. Verify that the battery is fully charged or close to fully charged.

    2. Important: Allow the engine to warm up to normal operating temperature.

  2. Stop the engine and remove the four spark plugs.

    3. Object Number: 262497 Size: SH
  3. Disconnect the electrical connectors at both ignition coils (1,2).

    4. Object Number: 56314 Size: SH
  4. Remove the Main Relay (1) from the Relay Box (2).

    5. Object Number: 166114 Size: SH
  5. Install a compression gage (2) into a spark plug hole.
  6. Depress the clutch pedal (on vehicles that are equipped with a manual transmission).
  7. Depress the accelerator pedal to the floor for a wide open throttle.
  8. Crank the engine through four compression strokes for each cylinder being tested.

    9. Important: The maximum allowable compression pressure difference between any two cylinders is 100 kPa (15 psi).

  9. Measure the highest pressure reading on the compression gage.
    10.  - The standard compression pressure is 1,350 kPa (192 psi).
     - The minimum allowable compression pressure is 1,100 kPa (156 psi).
  10. Repeat the compression test procedures for the remaining three cylinders.
  11. Remove the compression gage from the engine.
  12. Install the four spark plugs.

    13. Object Number: 262497 Size: SH
  13. Reconnect the electrical connectors at both ignition coils (1,2).

    14. Object Number: 56314 Size: SH
  14. Reconnect the Main Relay (1) to the Relay Box (2).
  15. Inspect for the following conditions:
    16.  - Normal operation
     - The pistons, piston rings and valves are operating normally if the cylinder compression pressure increases quickly and evenly to the compression standard (1,500 kPa (218 psi).
     - Faulty piston rings
     - The following actions indicate that the piston rings are faulty:
       - The cylinder compression is low on the first stroke.
       - The cylinder compression increases on the following strokes but does not reach the compression standard.
       - Add oil in order to improve the compression pressure.
     - Faulty valves
     - The following actions indicate that the valves are faulty:
       - The cylinder compression is low on the first stroke.
       - The cylinder compression does not increase on the following strokes.