Compression Pressure Inspection: Notes

NOTE: If the there is lack of power, excessive oil consumption or poor fuel economy, measure the compression pressure.

Warm up and stop engine.
Allow the engine to warm up to normal operating temperature.
Disconnect the ignition coil connectors and the spark plug cables. (Refer to IGNITION SYSTEM )

Fig 1: Identifying Ignition Coil Connectors And Spark Plug Cables
Courtesy of KIA MOTORS AMERICA, INC.
Remove the spark plugs.
Using a 16mm plug wrench, remove the 4 spark plugs.
Check the cylinder compression pressure.
1. Insert a compression gauge into the spark plug hole.
  
  Fig 2: Checking Cylinder Compression Pressure
  Courtesy of KIA MOTORS AMERICA, INC.
2. Fully open the throttle.
3. While cranking the engine, measure the compression pressure.
  NOTE: Always use a fully charged battery to obtain engine speed of 250rpm or more.
4. Repeat step 1) through 3) for each cylinder.
  NOTE: This measurement must be done in as short a time as possible.
  
  Compression pressure (1.6 CVVT)
  
  Standard : 1, 422kPa (14.5kg/cm² , 206psi) (250~400 rpm)
  
  Minimum : 1, 275kPa (13.0kg/cm² , 185psi)
  
  Difference between each cylinder :
  
  98kPa (1.0kg/cm² , 14psi) or less
5. 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 step 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.
Reinstall the spark plugs.
Connect the ignition coil connectors and the spark plug cables. (Refer to IGNITION SYSTEM )