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Home >> Kia >> 2021 >> Rio LX >> Repair and Diagnosis (Single Page) >> Engine Mechanical >> Mechanical >> Engine Mechanical System - General Information >> Compression Test >> Compression Pressure Inspection

Compression Pressure Inspection

NOTE: If the there is lack of power, excessive oil consumption or poor fuel economy, measure the compression pressure.
  1. Warm up and stop engine.

    Allow the engine to warm up to normal operating temperature.

  2. Remove the engine cover.

    (Refer to Engine and Transaxle Assembly - "ENGINE COVER ")

  3. Disconnect the injector connectors (A).
    G13704007Courtesy of KIA MOTORS AMERICA, INC.
  4. Remove the ignition coil.

    (Refer to Engine Electrical System - "IGNITION COIL ")

  5. Remove the spark plugs.

    Using a 16mm plug wrench, remove the 4 spark plugs.

    (Refer to Engine Electrical System - "SPARK PLUG ")

  6. Check the cylinder compression pressure.
    1. Insert a compression gauge into the spark plug hole.
      G13704008Courtesy of KIA MOTORS AMERICA, INC.
    2. Set the throttle plate in the wide-open position.
    3. While cranking the engine, measure the compression pressure.
      NOTE: Always use a fully charged battery to obtain engine speed of 200 RPM or more.
    4. Repeat step  1) through  3) for each cylinder.
      NOTE: This measurement must be done in as short time as possible.

      Compression pressure 

      Standard: 1225.83 kPa (12.5 kg/cm2 , 177.79 psi) (200 - 250 RPM)

      Maximum: 1098.34 kPa (11.2 kg/cm2 , 159.30 psi)

      Difference between each cylinder:

      98 kPa (1.0 kg/cm2 , 14 psi) or less

    5. If the cylinder compression in one or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat step  1) through  3) for cylinders with low compression.
      • If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.
      • If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.
  7. Install the spark plugs.

    (Refer to Engine Electrical System - "SPARK PLUG ")

  8. Install the ignition coil.

    (Refer to Engine Electrical System - "IGNITION COIL ")

  9. Install the injector connectors (A).
    G13704009Courtesy of KIA MOTORS AMERICA, INC.
  10. Some DTCs may exist after the inspection test and may need to be manually cleared with KDS.
  11. Install the engine cover.

    (Refer to Engine and Transaxle Assembly - "ENGINE COVER ")

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