Komatsu F30791, Shop Manual

Page: 143 / 298

MEASUREMENT OF THE COMPRESSION PRESSURE
20-27
TESTING AND ADJUSTMENTS MEASUREMENT OF THE COMPRESSION PRESSURE
.
While measuring the compression, take care not
to get entangled in the cooling fan, the alternator
belt, or in other rotating parts.
.
Check all cylinders.
H Test conditions:
. Engine: at working temperature.
.
Hydraulic oil: 45 ± 55 ëC.
.
Battery: fully charged.
. Valve clearance: adjusted
(See «ADJUSTMENT OF VALVE CLEARANCE»).
.
Air filter functioning properly.
1 - Remove the clamp (1) and disconnect the high-pres-
sure tube (2).
2 - Remove the nozzle holder (3) of the cylinder to be
checked.
3 - Disconnect the connector (4) of the engine-stopping
solenoid and close the fuel cock (5).
4 - Turn the engine over a few times, using the starting
motor.
5 - Mount the adapter B2 and connect the test pressure
gauge B1 .
H Check that the seal is mounted in the adapter,
and that it is undamaged.
6 - Turn the engine using the starting motor and read the
compression value.
H Read the compression value when the pressure
gauge has stabilised.
H While reading the compression, also check the
engine rpm using the tachometer C1 or C2 . If
the speed does not correspond with the control
value, check it against the diagram.
H Compression value:
Normal: PC20R-8: 32 w 1 kg/cm
2
at 250 rpm
PC27R-8: 31 w 1 kg/cm
2
at 250 rpm
Minimum permissible:
PC20R-8: 26 w 1 kg/cm
2
at 250 rpm
PC27R-8: 25 w 1 kg/cm
2
at 250 rpm
H Maximum difference between the cylinders:
2 ± 3 kg/cm
2
7 - After the reading, re-assemble the nozzle holder (3),
and reconnect the high- pressure tube (2) and the
connector (4).
Nut that secures the nozzle: 7.84 w 0.98 Nm
High-pressure coupling: 31.85 w 2.45 Nm
PC20R-8 PC27R-8
RKPA2150
3
2
1
RKPA2160
5
4
B
1
C
1
B
2
RKP06370
RKP06521
35
40
30
25
20
200 250 300 350 400
Engine speed (giri/min)
Compression pressure (kg/cm
2
)
PC27R PC20R