Doosan DX60R Shop Manual page 445

Troubleshooting by Measuring
Compression Pressure
Compression pressure drop is one of the major causes of
increasing blow-by gas (engine oil contamination or increased
engine oil consumption as a resultant phenomenon) or starting
failure. The compression pressure is affected by the following
factors:
1. Degree of clearance between the piston and cylinder
2. Degree of clearance at the intake / exhaust valve seat
3. Gas leak from the nozzle gasket or cylinder head gasket
The pressure will drop due to increased parts wear. Pressure
drop reduces the durability of the engine.
A pressure drop may also be caused by a scratched cylinder or
piston, dust entrance from the dirty air cleaner element or a
worn or broken piston ring. Measure the compression pressure
to determine the condition of the engine.
Compression Pressure Measurement Method
1. Warm up the engine.
2. Stop the engine. Remove the high-pressure fuel injection
lines as an assembly from the engine. Remove the fuel
injector from the cylinder to be measured. See "Removal
of Fuel Injectors" on page -194
3. Remove the valve cover assembly. See "Removal of Valve
Cover" on page -109 Remove the fuel injector from the
cylinder to be tested. See "Removal of Fuel Injectors" on
page -194
4. Turn off the fuel supply valve in the fuel supply line.
Disconnect the fuel injection pump stop solenoid at the
connector. This prevents the fuel injection pump from
injecting fuel during compression testing.
5. Before installing the compression gauge (1, Figure 416) 2
valve engine, (1, Figure 417) 4 valve engine) adapter,
crank the engine with the stop solenoid disconnected for a
few seconds to clear the cylinder of any residual fuel.
6. Install a nozzle seat at the tip end of the compression
gauge adapter. Install the compression gauge and the
compression gauge adapter at the cylinder to be
measured.
7. Crank the engine until the compression gauge reading is
stabilized.
Engine
Figure 416
SP001693
Page 265