GMC T-Series 1999, Owner'S Manual

Page: 51 / 344

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2-15
Avoid Unnecessary Idling of the
Diesel Engine
If the engine idles too long, the temperature of the
engine coolant will fall below the operating range. Low
engine operation temperature causes several conditions
which affect engine operation and reduce engine life.
Incomplete combustion of fuel in a cold engine causes
crankcase dilution and forms lacquer and gummy
deposits on valves, pistons and rings.
It also causes rapid accumulation of sludge within
the engine.
Checks Before Operating
The engine should be permitted to go through a
warm
-
up period. Operate at a minimum of 600 rpm
during warm
-
up period. During this period and during
operation, the following observations should be made.
1. Observe the oil pressure gage. If the oil pressure fails
to rise within 10 seconds after the engine starts, stop
the engine and determine the cause. Outside
temperature below 32
_F (0_C) will cause oil
pressure to rise more slowly.
2. Observe the engine coolant temperature gage.
If the gage reaches the hot area, stop the engine
and determine the cause of overheating.
3. If you have air brakes, observe the dual
-
needle air
pressure gage in the instrument cluster. The gage
should register at least 105 psi (720 kPa) for both
service systems before you try to move the vehicle.
When air pressure is below 60 psi (420 kPa), the
warning light will light and an alarm buzzer will
sound. If the air pressure fails to build up during the
engine warm
-
up period or if pressure should drop,
stop the engine and determine the cause before
moving the vehicle.
4. When the ignition switch is turned to ON, the
generator warning light in the instrument cluster will
light. The light should go out when the engine is
running above curb idle speed. If the light does not
go out when the engine starts, or comes on during
normal operation, have the charging system checked.
The warning light indicates if the generator is not
charging, and not the condition of the battery.