Checking Compression Pressure

Warm up engine thoroughly.
Release fuel pressure. Refer to [FUEL PRESSURE CHECK: QR25DE ]
Disconnect fuel pump fuse to avoid fuel injection during measurement.

Fig 1: Identifying Fuel Pump Fuse And IPDM E/R
Courtesy of SUZUKI OF AMERICA CORP.
Remove spark plug from each cylinder. Refer to [SPARK PLUG: REMOVAL AND INSTALLATION ]
Connect engine tachometer (not required in use of SDT).
Install compression tester with an adapter into spark plug hole.

Fig 2: Installing Compression Tester With An Adapter Into Spark Plug Hole
Courtesy of SUZUKI OF AMERICA CORP.
- Use the adapter whose pick 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.
  
  Fig 3: Identifying Adapter Diameter
  Courtesy of SUZUKI OF AMERICA CORP.

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:

COMPRESSION PRESSURE SPECIFICATIONS

Unit: kPa (kg/cm² , psi) /rpm
Standard	Minimum	Differential limit between cylinders
1, 304 (13.3, 189) / 250	1, 108 (11.3, 161) / 250	100 (1.0, 14) / 250

CAUTION: Always use fully a charged battery to obtain the specified engine speed.

If the engine speed is out of the 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 the 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, 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 gasket is leaking. In such a case, replace cylinder head gasket.

After inspection is completed, install removed parts.
Start engine, and make sure that engine runs smoothly.
Perform trouble diagnosis. If DTC appears, erase it.