engine GMC C-SERIES 1999 User Guide

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2-12 Fast Idle System (Electronically Controlled
Caterpillar

Diesel and Gasoline Engines)
If your vehicle is equipped with an electronically
controlled diesel engine, it has both automatic and
manual fast idle capabilities.
Automatic Fast Idle System
(Caterpillar

Diesel Engine Only)
The automatic fast idle feature will engage whenever
you start your vehicle and the engine is below the preset
operating temperature. This will help decrease engine
warm
-up time.
Idle speed will then return to normal under any of the
following conditions:

The engine reaches the preset operating temperature.

The brake pedal is pressed.

The trailer brake hand lever (if equipped) is applied.

The manual transmission clutch pedal is pressed or,
the automatic transmission (if equipped) is shifted
from NEUTRAL (N) or PARK (P).

The vehicle speed exceeds approximately
10 mph (16 km/h).

When the fast idle switch is pressed a second time.Manual Fast Idle System
(Caterpillar
 Diesel and Gasoline Engines)
The manual fast idle switch
is located on the lower
portion of the instrument
panel just to the left of the
steering wheel.
This system can be used to increase your engine idle
speed whenever the following conditions are met:

The brake pedal is not pressed.

The trailer brake hand lever (if equipped) is not applied.

The vehicle speed is below approximately
10 mph (16km/h).

The manual transmission (if equipped) clutch pedal
is not pressed or, the automatic transmission
(if equipped) is in NEUTRAL (N).
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The manual fast idle feature is activated by pressing the
switch on the instrument panel. When the switch is
pressed again, or any of the previous conditions are not
met, manual fast idle will be deactivated.
Manual fast idle can be used to set any desired idle
speed. To set a new temporary engine idle speed:
1. Make sure all of the previously described conditions
are met.
2. Press the accelerator pedal to the desired engine speed.
3. Momentarily press the manual FAST IDLE switch.
The temporary idle speed will be set. This new rpm
level will be remembered by the system until either the
ignition is turned to OFF or a new idle speed is set.
Radiator Shutters -- Caterpillar

(If Equipped)
Radiator shutters aid engine warm-up by blocking the
airflow through the radiator and charge the air cooler to
conserve heat in cold conditions.
The radiator shutters on your vehicle (if equipped)
operate automatically. When the ignition switch is in
RUN or START and the engine temperature is below
195F (90C), the shutters will close, blocking the flow
of air through the radiator and charge the air cooler.When the engine temperature reaches 195F (90C), the
shutters will open to the normal operating position.
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.
During this warm
-up period, check your warning lights
and gages:

If oil pressure doesn't begin to rise within 15 seconds
of starting, stop the engine and find the cause.

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.

If you have air brakes, the dual
-needle air pressure
gage should read 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
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).
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The charging system light should come on when the
ignition switch 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.)

The voltmeter charge indicator gage tells you the
condition of your battery's charge. The gage should
be in the center area during engine operation. The
red area on the left indicates an undercharge
condition; the red area on the right indicates an
overcharge. If the gage is in either red area, have the
battery and charging system checked right away.
NOTICE:
Don't allow the engine to operate at low idle for
more than five minutes. This can cause low
engine operating temperatures which can affect
engine operation and reduce engine life. Engine
idle speed should be increased to 1200 rpm
whenever extended idle is required. Once started,
the engine should be placed under load to allow
the engine coolant temperature to reach
150F (66C) before shutting off the engine.
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Engine Coolant Heater (If Equipped)
If your vehicle has this
feature, the plug
-in
receptacle is located behind
the front bumper as shown,
or in the component box
on the driver's side of
the vehicle.
In very cold weather, 0
F (
-18
C) or colder, the engine
coolant heater can help. You'll get easier starting and
better fuel economy during engine warm
-up. Usually,
the coolant heater should be plugged in a minimum of
four hours prior to starting your vehicle.
To Use the Engine Coolant Heater
1. Turn off the engine.
2. Find the plug
-in receptacle (either behind the front
bumper or in the component box).
3. Plug a heavy
-duty, three-prong extension cord
(rated for at least 15 amps) into the vehicle's plug
-in
receptacle first. Then plug the extension cord into a
normal, grounded 110
-volt AC outlet.
CAUTION:
Plugging the cord into an ungrounded outlet
could cause an electrical shock. Also, the wrong
kind of extension cord could overheat and cause
a fire. You could be seriously injured. Plug the
cord into a properly grounded three
-prong
11 0
-volt AC outlet. Use a heavy-duty three-prong
extension cord rated for at least 15 amps.
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4. Before starting the engine, be sure to unplug the cord.
How long should you keep the coolant heater plugged
in? The answer depends on the outside temperature.
Above 32
F (0
C), the coolant heater is not required.
From 32
F to
-10
F (0
C to -23
C), keep the
coolant heater plugged in at least two hours. Below
-10
F (-23
C), keep the coolant heater plugged in for
a minimum of eight hours or overnight. It will not harm
either the coolant heater or the vehicle to leave the
coolant heater plugged in longer than the times stated.
Be sure to remove and store the cord before starting the
engine. See ªDiesel Fuel Requirements and Fuel
Systemº in the Index for information on what fuel to use
in cold weather.
Diesel Engine Exhaust Brake
The exhaust brake is available on vehicles equipped
with a diesel engine and air brakes (or an air
compressor). It is located in the exhaust system.
The switch is on the upper
right side of the instrument
panel and turns the exhaust
brake on and off.
The exhaust brake indicator light is on when the exhaust
brake is in use.
The exhaust brake is used to help slow the vehicle and
may assist the vehicle's foundation brakes. The use of the
exhaust brake will assist the braking of the vehicle and
prolong the life of the foundation brake lining material.
When using the exhaust brake, the proper gear range
selection is important. The exhaust brake will be most
effective if the gear range selected is the lowest possible
range that does not allow the engine rpm to go more than
200 rpm above rated (full load) rpm as shown on the
Engine Information Plate. (Do not exceed 2900 rpm.)
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The accelerator and clutch pedals must be released in
order for the exhaust brake to engage. Whenever the
exhaust brake is active, the light in the switch will be on.
Do not use the exhaust brake when running the engine at
idle during warm
-up or other extended periods.
Prolonged use of the exhaust brake during idling will
cause the engine to overheat.
CAUTION:
Be careful when using the exhaust brake or you
could lock the wheels and lose control of the
vehicle. Operators not familiar with an exhaust
brake should not use this brake on slippery
surfaces before learning to use it on dry surfaces.
If the vehicle's wheels begin to lock when using
the exhaust brake on slippery surfaces, switch the
exhaust brake off immediately. The exhaust
brake will turn off if the anti
-lock brake system
is activated.
Tw o-Speed Rear Axle Electric Shift
Control (If Equipped)
If your vehicle has this feature, you'll find a label (or
labels) on the ceiling above the windshield or in another
place near the driver that show how to use it. Be sure
to follow the directions carefully. Use the following
directions based on the type of shift control you have.
Automatic Transmission
The switch for the rear axle
shift control is on the shift
tower to the right of the
shift lever.
When the switch is up, the rear axle is in the high range.
Push it down to get the low range.
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The two-speed axle should be in low range when you
park the vehicle. Apply the parking brake, shift to
PARK (P) or NEUTRAL (N) and shut off the engine.
To operate off
-road or under a heavy load, shift into low
range when the vehicle is standing still and then operate
the transmission normally.
On the highway, with the axle in low range and
transmission in top gear, you may shift the axle to high
range by raising the switch and releasing the accelerator
momentarily. Re
-apply the accelerator after your shift.
Under light load conditions, first shift the axle into the
high range with the vehicle at a standstill and then
operate the transmission normally.
Manual Transmission
The switch for the rear axle
shift control is on the shift
lever. When the switch is
up, the rear axle is in the
high range. Push it down to
get the low range.
The two
-speed axle should be in low when you park the
vehicle. You'll need to engage the transmission, even
move the vehicle a little, to be sure the axle is in the low
range. Then apply the parking brake, shift into
NEUTRAL and shut off the engine.
Also, always start the vehicle in motion with the
two
-speed axle in the low range. When you upshift the
rear axle from low to high, move the switch up for the
high range, disengage the clutch, pause, engage the
clutch and then press down on the accelerator. When
you shift the axle down from high to low, you don't
have to clutch. Just move the switch down to low,
release the accelerator and then quickly apply it again.
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2-19 Air Shift Control
(Manual Transmissions Only)
The lever for the rear axle
shift control is either at the
lower right corner of the
instrument panel or on the
shift lever.
When the lever is moved to HI, the rear axle will be in
the high range. Switch it to LOW to get the low range.
The two
-speed axle should be in LOW when you park
the vehicle.
You'll need to engage the transmission, even moving the
vehicle a little, to be sure the axle is in the low range.
Then apply the parking brake, shift into NEUTRAL and
shut off the engine.Also, always start the vehicle in motion with the
two
-speed axle in the LOW position. When you upshift
the rear axle from LOW to HI, move the lever to the
HI position, disengage the clutch, pause, engage the
clutch and then press down on the accelerator. When
you shift the axle down from HI to LOW, you don't
have to clutch. Just move the lever to LOW, release the
accelerator and then quickly press it down again.
Air Suspension (If Equipped)
Your vehicle may be equipped with the Hendrickson
HAS Series single
-axle air suspension which is designed
for single
-axle on-highway use. This feature is available
in the 19,000 lb. capacity and as a low profile option for
operations which require extra cubic capacity and a
reduced deck height.
With this air suspension system, the ride height is set
during vehicle assembly so that the vehicle has a constant
frame height. The system will then increase or decrease
air pressure in the air springs to maintain this height.
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Air Suspension Dump Control (If Equipped)
If your vehicle is equipped with the Hendrickson HAS
Series single
-axle air suspension, you may have this
control. The air suspension dump control allows the
operator to lower the deck height approximately
4.5 inches (11.5 cm) from the normal frame height.
The switch to deflate and
inflate the air suspension is
located on the upper left
side of the instrument panel
above the driver's side vent.
The light in the switch will be illuminated whenever the
switch is in the ªdumpedº position.
Automatic Transmission Operation
We build vehicles with four, five and six-speed
automatic transmissions. This part of the manual covers
the basics of these. With some of the transmissions, you
will find another manual in your vehicle that goes into
more detail. On the ceiling, in front of and above the
driver, or in some other place near the driver, you will
see a label that describes important operating facts about
the automatic transmission in your vehicle. Make sure
you follow the instructions on this label.
You may have a PARK (P) position for your shift lever.
This position locks your rear wheels. It is the best
position to use when you start your engine because your
vehicle can't move easily.
All vehicles equipped with automatic transmissions
can be started in PARK (P), if equipped, or in
NEUTRAL (N). When you shift out of NEUTRAL (N),
you may have to hold in a push button on the shift lever
or lift up on a release handle as you shift. See the
Allison Automatic Transmission Operator's Manual in
your vehicle for more information about this.
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CAUTION:
It is dangerous to get out of your vehicle if the
shift lever is not fully in PARK (P) with the
parking brake firmly set. Your vehicle can roll.
Don't leave your vehicle when the engine is
running unless you have to. If you have left the
engine running, the vehicle can move suddenly.
You or others could be injured. To be sure your
vehicle won't move, even when you're on fairly
level ground, always set your parking brake and
move the shift lever to PARK (P).
See ªShifting Into PARK (P)º in the Index.
CAUTION:
Shifting out of PARK (P) or NEUTRAL (N) while
your engine is ªracingº (running at high speed) is
dangerous. Unless your foot is firmly on the
brake pedal, your vehicle could move very
rapidly. You could lose control and hit people or
objects. Don't shift out of PARK (P) or
NEUTRAL (N) while your engine is racing.
Automatic Transmission Third Gear Hold
(If Equipped)
If you have this feature, your range selector has a
ª2
-3º position. You can't shift up to the next higher
gear when the transmission is in this position unless
your engine
-governed speed is exceeded, such as when
going downhill.
This feature is useful for certain load and traffic
conditions or when plowing snow. See the Allison
Automatic Transmission Operator's Manual in your
vehicle for further information.
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