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Home >> Mazda >> 2003 >> Protege5 Standard >> Repair and Diagnosis (Single Page) >> Engine Mechanical >> Mechanical >> Engine Mechanical Service Information >> Compression Inspection >> Notes

Compression Inspection: Notes

WARNING:
  • Hot engines and oil can cause severe burns. Be careful not to burn yourself during removal/installation of each component.
  1. Verify that the battery is fully charged.
    • Recharge it if necessary.
  2. Warm up the engine to the normal operating temperature.
  3. Stop the engine and allow it to cool off for about 10 min. 
  4. Perform fuel pressure release. See FUEL SYSTEM PRESSURE RELEASE . Leave the fuel pump relay removed.
  5. Remove the ignition coils. (See IGNITION COIL PACK .)
  6. Remove the spark plugs.
  7. Connect a compression gauge into the No.1 spark plug hole.
  8. Fully depress the accelerator pedal and crank the engine.
  9. Note the maximum gauge reading.
  10. Inspect each cylinder as above.
    • If the compression in one or more cylinders is low or the compression difference between cylinders exceeds the maximum, pour a small amount of clean engine oil into the cylinder and recheck the compression.
      • If the compression increases, the piston, the piston rings, or cylinder wall may be worn and overhaul is required.
      • If the compression stays low, a valve may be stuck or improperly seated and overhaul is required.
      • If the compression in adjacent cylinders stays low, the cylinder head gasket may be damaged or the cylinder head distorted and overhaul is required.
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