Nissan Armada 2025-2026 Service and Repair Manual: Compression Pressure

Inspection

WARNING:

Jacking up or lift up the vehicle may the vehicle height to go down which cause a personal injury and/or damage to the air suspension component parts. Refer to Precaution for when Jacking and Lifting Up the vehicle with Electronic Air Suspension System.

1. Warm up engine thoroughly. Then, stop it.

2. Release fuel pressure. Refer to Work Procedure.

3. Disconnect fuel pump fuse from IPDM E/R to avoid fuel injection during measurement.

4. Remove engine cover. Refer to Removal and Installation.

5. Remove ignition coil and spark plug from each cylinder.

6. Connect engine tachometer (not required in use of CONSULT).

7. Install compression gauge with an adapter (commercial service tool) onto spark plug hole.

   

   • Use the adapter whose picking up end inserted to spark plug hole is smaller than 20 mm (0.79 in) in diameter. Otherwise, it may be caught by cylinder head during removal.

     

     : 20 mm (0.79 in)

8. With accelerator pedal fully depressed, turn ignition switch to “START” for cranking. When the gauge pointer stabilizes, read the compression pressure and the engine rpm. Perform these steps to check each cylinder.

   Compression pressure

   CAUTION:

   • Measure a six-cylinder under the same conditions since a measurement depends on measurement conditions (engine water temperature, etc.).

   • Always use a fully changed battery to obtain the specified engine speed.

   • If the engine speed is out of the specified range, check battery liquid for proper gravity. Check the engine speed again with normal battery gravity.

   • If compression pressure is below the minimum value, check valve clearances and parts associated with combustion chamber (valve, valve seat, piston, piston ring, cylinder bore, cylinder head, cylinder head gasket). After checking, measure compression pressure again.

   • If a cylinder has low compression pressure, pour a small amount of engine oil into the spark plug hole of the cylinder to recheck it for compression.

     • If the added engine oil improves the compression, piston rings may be worn out or damaged. Check piston rings and replace if necessary.

     • If the compression pressure remains at low level despite the addition of engine oil, valves may be malfunctioning. Check valves for damage. Replace valve or valve seat accordingly.

   • If two adjacent cylinders have respectively low compression pressure and their compression remains low even after the addition of engine oil, cylinder head gaskets are leaking. In such a case, replace cylinder head gaskets.

9. After inspection is completed, install removed parts.

10. Start the engine, and check that the engine runs smoothly.

11. Perform trouble diagnosis. If DTC appears, erase it.