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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 1819 (Engine Mechanical - 3.5L (L66)) >> Diagnostic Information and Procedures >> Engine Compression Test >> Tools Required

Tools Required

WARNING: This page is about a different car, the 2007 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

SA9127E  Gage Bar Set

    Fig 1: Checking Engine Compression
    GM897249Courtesy of GENERAL MOTORS CORP.
  1. Warm up the engine to a normal operating temperature of 98°C (208° F).
  2. Turn the ignition switch OFF.
  3. Remove the ignition coils. Refer to Valve Rocker Arm Cover Removal - Left Side  and Valve Rocker Arm Cover Removal - Right Side .
  4. Remove the spark plugs.
  5. Attach the adapter (1), hose (2) and compression gage (3) to a spark plug hole.
  6. Connect a tachometer.
  7. Connect the scan tool.
  8. Turn the ignition switch to the ON position.
  9. Using the scan tool, command the injectors all off.
  10. Depress the accelerator pedal to open the throttle fully.
  11. Crank the engine with the starter motor and measure the compression.
  12. Perform the measurement on each cylinder and compare the readings.

    Specification: 

    • Compression pressure: minimum 990 kPa (145 psi) at 200 RPM
    • Maximum compression variation: 200 kPa (28 psi)

  13. If the compression is not within specifications, inspect for the following conditions and measure the compression again.
    • Improperly adjusted valves
    • Improperly positioned timing belt and sprockets
    • Damaged or worn valves or seats
    • Damaged cylinder head gasket
    • Damaged or worn piston rings
    • Damaged or worn piston and cylinder bore
  14. Using the scan tool, perform the PCM Reset Procedure to return the fuel injectors to normal operation.