GMC 2003 C4C042, Owner'S Manual

Page: 102 / 386

2-27
Engine Checks Before Operating
When you’ve started your engine, let it run for 20 to
30 seconds before you put a load on the engine. But
don’t leave the vehicle while the engine is running.
Avoid unnecessary idling of diesel engine equipped
vehicles.
If the engine idles too long, the temperature of the
engine coolant will fall below the normal operating
range. Low engine operating temperature causes several
conditions which affect engine operation and reduce
engine life.
The engine should be permitted to go through a
warm
-
up period. Operate the vehicle at a minimum of
600 rpm during the warm
-
up period. During this period
and during operation, the following observations should
be made.
During this warm
-
up period, check your warning lights
and gages:
D If oil pressure doesn’t begin to rise within
15 seconds of starting, stop the engine and
find the cause.
D If the engine coolant temperature gage needle goes
into the hot area on the gage, stop the engine and
find the cause of the overheating.
D If you have air brakes, the dual
-
needle air pressure
gage should read at least 115 psi (790 kPa) for both
service systems before you try to move the vehicle.
When air pressure is below 60 psi (420 kPa), the
LOW AIR light will come on and you will hear a
tone alarm. If the pressure doesn’t build up or
drops during warm
-
up, stop the engine and find
the cause before you try to move the vehicle.
Recommended air pressure before actually driving
away is 120 psi (830 kPa).
D The charging system light should come on when
the ignition key is turned to RUN or START and
should go out when the engine is running above idle.
If the light doesn’t go out or comes back on during
normal engine operation, have the charging system
checked right away. (This light tells you if the
generator is not charging; it doesn’t reflect the
condition of the battery.)