Engine Compression: Inspection

NOTE: If 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.
REMOVE SPARK PLUGS (See ON-VEHICLE INSPECTION )

Fig 1: Inspecting Cylinder Compressor Pressure
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
CHECK CYLINDER COMPRESSION PRESSURE
1. Insert a compression gauge into the spark plug hole.
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 250 RPM or more.
4. Repeat steps ( a) through (c) for each cylinder.
  NOTE: This measurement must be done in as short a time as possible.
  1. Compression pressure:
  2. 1,324 kPa (13.5 kgf/cm ² , 192 psi) or more
  3. Minimum pressure:
  4. 981 kPa (10.0 kgf/cm ² , 142 psi)
  5. Difference between each cylinder:
  6. 98 kPa (1.0 kgf/cm ² , 14 psi) or less
5. If the cylinder compression in one or more cylinders is low, pour small amount of engine oil into the cylinder through the spark plug hole and repeat steps ( a) through ( c) for cylinders with low compression.
  - If adding oil helps the compression, chances are 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.
REINSTALL SPARK PLUGS (See ON-VEHICLE INSPECTION )