Section 494 (Engine Mechanical): Compression: Inspection

HINT:

If 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 IGNITION COILS (See  IGNITION COIL  ) 
3. REMOVE SPARK PLUGS 
4. INSPECT 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.

      HINT:

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

      Fig 1: Measuring Compression Pressure

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   4. Repeat steps ( a) through ( c) for each cylinder.
      NOTE: This measurement must be done in as short a time as possible.
      • Compression pressure: 1.300 kPa (13.8 kgf/cm ²  , 196 psi) 
      • Minimum pressure: 1.00 MPa (10 kgf/cm ²  , 142 psi) 
      • Difference between each cylinder: 100 kPa (1.0 kgf/cm ²  , 14 psi) 
   5. If the cylinder compression in one more cylinders is low, pour a 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, it is likely 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 through the gasket.
5. REINSTALL SPARK PLUGS 
6. REINSTALL IGNITION COILS (See  IGNITION COIL  )