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 injector extension connector (A) and ignition coil connectors (B).

Fig 1: Injector Extension Connector & Ignition Coil Connectors
Courtesy of KIA MOTORS AMERICA, INC.
Remove ignition coils (A).

Fig 2: Ignition Coils
Courtesy of KIA MOTORS AMERICA, INC.
Remove spark plugs.
Using a 16 mm plug wrench, remove the 4 spark plugs.
Check cylinder compression pressure.
1. Insert a compression gauge into the spark plug hole.
  
  Fig 3: 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 200 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, 324 kPa (13.5 kgf/cm² , 192 psi) / 200 ~ 250 RPM
  
  Minimum pressure:
  
  1, 177 kPa (12.0 kgf/cm² , 171 psi)
  
  Difference between each cylinder:
  
  100 kPa (1.0 kgf/cm² , 15 psi) 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 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.
Reinstall spark plugs.
Install ignition coils.
Connect the injector extension connector and ignition coil connectors.
Some DTC's may exist after the inspection test and may need to be manually cleared with GDS.