Compression Test

Compression Pressure Test

If engine power is insufficient, oil consumption is excessive, or fuel economy is poor, measure the compression pressure.

1. 1
   Warm up the engine to normal operating temperature (80 to 95 °C).
2. 2
   Remove the expansion tank. (Refer to Intake and Exhaust System - "Expansion Tank")
3. 3
   Remove the ignition coils. (Refer to Engine Electrical System - "Ignition Coil")
4. 4
   Remove the spark plugs. (Refer to Engine Electrical System - "Spark Plug")
5. 5
   Check the compression pressure in the cylinder.

   1. Insert the compression gauge into the spark plug hole.
   2. Fully open the throttle valve.
   3. Crank the engine over 7 times to measure the compression pressure.

      Always use a fully charged battery to obtain an engine speed of 250 rpm or more.

   4. Repeat steps 1) through 3) for each cylinder.

      This measurement must be done as quickly as possible.

      Compression pressure: 1029 kPa (10.5 kgf/cm², 149 psi) (250–400 rpm) Minimum pressure: 882 kPa (9.0 kgf/cm², 128 psi) Difference between each cylinder: 98 kPa (1.0 kgf/cm², 14 psi) or less
   5. If compression is low in one or more cylinders, pour a small amount of engine oil into the cylinder through the spark plug hole, then repeat steps 1) through 3) for the cylinders with low compression.

      a.	If adding oil improves compression, the piston rings and/or cylinder bore are likely worn or damaged.

      b.	If pressure remains low, a valve may be sticking or seating improperly, or there may be leakage past the head gasket.

6. 6
   Reinstall the spark plugs. (Refer to Engine Electrical System - "Spark Plug")
7. 7
   Install the ignition coils and ignition connectors. (Refer to Engine Electrical System - Ignition Coil)
8. 8
   Install the expansion tank. (Refer to Intake and Exhaust System - "Expansion Tank")