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Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 1040 (Engine Mechanical - QG18DE) >> Cylinder Head >> On-Vehicle Service >> Checking Compression Pressure

Checking Compression Pressure

WARNING: This page is about a different car, the 2004 Nissan Sentra. However, it is still accessible from the selected car via links, so may be relevant.
  1. Warm up the engine to full operating temperature.
  2. Turn the ignition switch OFF.
  3. Release the fuel pressure. Refer to FUEL PRESSURE RELEASE .
  4. Remove the ignition coils.
  5. Remove the spark plugs.
    • Clean the area around the spark plug with compressed air before removing the spark plug.
  6. Attach a compression tester to No. 1 cylinder.
    Fig 1: Attaching Compression Tester To No. 1 Cylinder
    G00774035Courtesy of NISSAN MOTOR CO., U.S.A.
    Fig 2: Identifying Compression Tester End Diameter
    G00774036Courtesy of NISSAN MOTOR CO., U.S.A.
  7. Depress the accelerator pedal fully to keep the throttle valve wide open.
  8. Crank the engine and record highest gauge indication.
  9. Repeat the measurement on each cylinder as shown above.
    NOTE: Always use a fully-charged battery to obtain specified engine speed.
    1. Compression pressure : kPa (kg/cm 2, psi)/rpm 
      1. Standard : 1,324 (13.5, 192)/350 
      2. Minimum : 1,157 (11.5, 168)/350 
      3. Maximum allowable difference between cylinders : 98 (1.0, 14)/350 
  10. If cylinder compression in one or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and retest compression.
    • If adding oil improves cylinder compression, piston rings may be worn or damaged. If so, replace piston rings after checking the piston and cylinder walls.
    • If pressure stays low, a valve may be sticking or seating improperly. Inspect and repair valve and valve seat. Refer to , "INSPECTION ", , "VALVE SEATS ". If valve or valve seat is damaged excessively, replace them.
    • If compression in any two adjacent cylinders is low and if adding oil does not improve compression, there is leakage past the gasket surface. If so, replace cylinder head gasket.
  11. Install spark plugs, ignition coils and fuel pump fuse.
  12. Erase DTC if any DTC appears. Refer to HOW TO ERASE EMISSION-RELATED DIAGNOSTIC INFO .
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