Engine Compression: Inspection

HINT:

If there is a 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 the normal operating temperature.

2. REMOVE SPARK PLUGS 

   (See  ON-VEHICLE INSPECTION  ) 

   Fig 1: Checking Cylinder Compression Pressure

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3. 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.

      HINT:

      Always use a fully charged battery to obtain the engine speed at 250 RPM or more.

   4. Repeat steps ( a) to ( c) for each cylinder.
      NOTE: This measurement must be done as quickly 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 lower than the specification, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat steps ( a) to ( c) for the cylinders.
      • If adding oil helps the compression, chances are that the piston rings and/or cylinder bore are worn or damage.
      • If the pressure stays low, a valve may be sticking or the seating is improper, or there may be leakage past the gasket.
4. REINSTALL SPARK PLUGS 
   1. (See  ON-VEHICLE INSPECTION  )