Checking Compression Pressure

WARNING: This page is about a different car, the 2004 Nissan Titan. However, it is still accessible from the selected car via links, so may be relevant.

Warm up engine thoroughly. Then, stop it.
Release fuel pressure. See FUEL PRESSURE RELEASE in BASIC DIAGNOSTIC PROCEDURES - TITAN article in ENGINE PERFORMANCE.
- Remove fuel pump fuse, and start engine. See FUSES & CIRCUIT BREAKERS - TITAN article in ELECTRICAL.
  - Ensure fuel pump fuse remains removed until the end of step 7) .
- After engine stalls, crank it two or three times to release all fuel pressure.
Remove ignition coil and spark plug from each cylinder.
Refer to SPARK PLUG (PLATINUM-TIPPED TYPE) .
Connect engine tachometer (not required in use of CONSULT-II).
Use a suitable tool and thread into spark plug hole.
With accelerator pedal fully depressed, turn ignition switch to "START" for cranking. When the gauge pointer stabilizes, read the compression pressure and engine RPM. Perform these steps to check each cylinder.

Fig 1: Compression Specification Table
Courtesy of NISSAN MOTOR CO., U.S.A.

Fig 2: Measuring Compression
Courtesy of NISSAN MOTOR CO., U.S.A.

CAUTION: Always use a fully charged battery to obtain specified engine speed.
- If the engine speed is out of specified range, check battery liquid for proper gravity. Check engine speed again with normal battery gravity.
- If compression pressure is below 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 the checking, measure compression pressure again.
- If some cylinders have low compression pressure, pour small amount of engine oil into the spark plug hole of the cylinder to re-check it for compression.
  - If the added engine oil improves the compression, the piston rings may be worn out or damaged. Check the piston rings and replace if necessary.
  - If the compression pressure remains at low level despite the addition of engine oil, the valves may be malfunctioning. Check the valves for damage. Replace the 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, the gaskets may be leaking, or valve in adjacent cylinders may be damaged. Inspect and repair as required.
Installation of the remaining components is in the reverse order of removal.
Start engine, and confirm that engine runs smoothly.
Perform trouble diagnosis. If DTC appears, erase it. See ENGINE CONTROL SYSTEM - TITAN article in ENGINE PERFORMANCE