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Compression Pressure: Notes

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 surge tank.
  3. Remove the ignition coil connectors (A) and ignition coils (B).
    Fig 1: Identifying Ignition Coil Connectors
    G07249552Courtesy of HYUNDAI MOTOR CO.
  4. Remove the spark plugs.

    Using a 16mm plug wrench, remove the 6 spark plugs.

  5. Check cylinder compression pressure.
    1. Insert a compression gauge into the spark plug hole.
    2. Fully open the throttle.
    3. After 7 times of cranking the engine, measure the compression pressure.
      NOTE: Always use a fully charged battery to obtain engine speed of 250 rpm or more.
    4. Repeat steps  1 through 3) for each cylinder.
      NOTE: This measurement must be done in as short a time as possible.

    Compression pressure: 

    1,225kPa (12.5kgf/cm2 , 177psi)

    Minimum pressure: 

    1,078kPa (11.0kgf/cm2 , 156psi)

    Difference between each cylinder: 

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

  6. If the cylinder compression in 1 or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat steps  1 through (3) for cylinders with low compression.
    1. If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.
    2. If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.
  7. Reinstall the spark plugs.
  8. Install the ignition coil and ignition coil connectors.
  9. Install the surge tank.
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