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Checking Compression Pressure: Notes

  1. Before checking the engine compression, check the engine oil level. Also check that the starter motor and battery are all in normal operating condition.
  2. Start the engine and wait until the engine coolant temperature reaches 80-95°C (176-205°F).
  3. Stop the engine and disconnect the spark plug cables.
  4. Remove the spark plugs.
  5. Crank the engine to remove any foreign material in the cylinders.
  6. Insert the compression gauge into the spark plug hole.
  7. Depress the accelerator pedal to open the throttle fully.
  8. Crank the engine and read the gauge.

    Standard value: 1, 275 kPa (13.0 kg/cm2 ), 185 psi)

    Limit: 1, 128 kPa (11.5 kg/cm2 , 164 psi)

    Fig 1: Checking Compression Pressure
    G00340173Courtesy of KIA MOTORS AMERICA, INC.
  9. Repeat steps 6 to 8 for all cylinders, making sure that the pressure difference for each of the cylinders is within the specified limit.

    Limit: 

    Max. 100 kPa (1.0 kg/cm2 , 14 psi) between cylinders

  10. If a cylinder's compression or pressure differential is outside the specification, add a small amount of oil through the spark plug hole, and repeat steps 6 to 9.
    1. If the addition of oil causes the compression to rise, it is possible that the piston ring is be worn.
    2. If the compression remains the same, valve seizure, poor valve seating or a compression leak in the cylinder head gasket are all possible causes.

      Tightening torque 

      Spark plug: 20-30 N.m (200-300 kg. cm, 14-22 lb. ft)

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