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Measurement Of Compression Pressure

WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.
  1. Warm up engine.
  2. Turn ignition switch OFF.
  3. Release fuel pressure.

    Refer to FUEL SYSTEM PRESSURE RELEASE .

  4. Disconnect fuel pump fuse to avoid injection during measurement.
    5. Fig 1: Identifying Fuel Pump Fuse
    G02032146Courtesy of NISSAN MOTOR CO., U.S.A.
  5. Remove engine cover.
  6. Remove air duct with air cleaner case.
  7. Remove harness connectors and harness brackets around ignition coils.
  8. Remove Electric throttle control actuator.
  9. Disconnect ignition coil with power transistor harness connectors, then remove ignition coils.
  10. Remove all spark plugs.
    • Clean area around plug with compressed air before removing the spark plug.
  11. Attach a compression tester to No. 1 cylinder.
    12. Fig 2: Attaching Compression Tester In Cylinder
    G02032148Courtesy of NISSAN MOTOR CO., U.S.A.
    Fig 3: Identifying Compressor Tester
    G02032149Courtesy of NISSAN MOTOR CO., U.S.A.
  12. Crank engine and record highest gauge indication.
  13. Repeat the measurement on each cylinder as shown above.
    • Always use a fully-charged battery to obtain specified engine speed. 
      Fig 4: Engine Speed Chart
      G02032147Courtesy of NISSAN MOTOR CO., U.S.A.
  14. If compression in one or more cylinders is low:
    1. Pour a small amount of engine oil into cylinders through spark plug holes.
    2. Retest compression.
    • If adding oil helps compression, piston rings may be worn or damaged. If so, replace piston rings after checking piston. 
    • If pressure stays low, a valve may be sticking or seating improperly. Inspect and repair valve and valve seat. (Refer to SDS,  VALVE   and  VALVE GUIDE  .) If valve or valve seat is damaged excessively, replace them. 
    • If compression stays low in two cylinders that are next to each other: 
    1. The cylinder head gasket may be leaking, or
    2. Both cylinders may have valve component damage. Inspect and repair as necessary.
  15. Install removed parts in reverse order of removal.
  16. Perform "Self-diagnosis Procedure" referring to SELF-DIAGNOSTICS if any DTC appears.
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