GMC C-SERIES 1999 Workshop Manual

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NOTICE:
Your engine is designed to work with the
electronics in your vehicle. If you add electrical
parts or accessories, you could change the way
the engine operates. Before adding electrical
equipment, check with your dealer. If you don't,
your engine might not perform properly.
If you ever have to have your vehicle towed, see
the part of this manual that tells how to do it
without damaging your vehicle. See ªTowing
Your Vehicleº in the Index.
Gasoline Engine Warm-Up
When you've started your engine, let it run for 20 or
30 seconds to warm up before you put a load on
the engine.
Drive at moderate speeds for the first few miles,
especially in cold weather. Running a cold engine at
high speed can damage it.
Restarting the Gasoline Engine While
Moving (Automatic Transmission)
If you have to restart the engine while the vehicle is
moving, you'll first have to shift the automatic
transmission to NEUTRAL (N). This safety feature
prevents starting the engine when the transmission is in
a drive gear.
Stopping the Gasoline Engine
Let your engine idle for a few seconds before turning it
off after you have finished driving your vehicle.
If you shift to NEUTRAL (N), set the parking brake.
If you shift to PARK (P), the auto
-apply feature will set
the parking brake.
If your vehicle has a two
-speed axle, put the range
selector in LOW. To be sure the axle has shifted into
LOW, engage the clutch and transmission the vehicle
may move slightly when you do this.
While your engine is idling before you turn it off, you
can make a list of any operational or handling concerns
to give to responsible maintenance personnel so they can
handle them right away.
Moisture will condense in a fuel tank that is almost
empty if the vehicle is not run for a while, even just
overnight under some conditions. So, it's always best to
refuel your vehicle at the end of each run.
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Starting Your Diesel Engine
If you have a Caterpillar diesel engine, also refer to
your Caterpillar
Operation & Maintenance Manual for
starting procedure.
To make starting easier in cold weather (below 32F or
0C), the proper viscosity engine oil should be used. It's
also best to heat the engine oil first. You can do this by
using an engine coolant heater. A GM Automatic Ether
Injection System aids cold weather starting.
NOTICE:
Your diesel engine has an electric air intake
heater system which reduces white smoke and
helps start the engine in cold weather. Do not
spray starting fluid into the air intake where it
can contact the heater elements.
If you don't have the GM Automatic Ether
Injection System, don't use starting fluid or
you could damage your engine. If you have the
GM system, use only GM approved starting fluid
that has been tested to establish compatibility
with the air inlet heater system.
NOTICE:
If you ever have to have your vehicle towed, see
the part of this manual that tells how to do it
without damaging your vehicle. See ªTowing
Your Vehicleº in the Index.
Restarting the Diesel Engine While Moving
(Automatic Transmission)
If you have to restart the engine while the vehicle is
moving, you'll first have to shift the automatic transmission
to NEUTRAL (N). This safety feature prevents starting
the engine when the transmission is in a drive gear.
Stopping the Diesel Engine
If you have a Caterpillar diesel engine, see your
Caterpillar
Operation & Maintenance Manual.
1. Set the parking brake and shift to NEUTRAL (N) or
PARK (P).
2. Turn the ignition switch key to OFF.
If your vehicle has a two
-speed axle, see ªRear Axle,
Tw o
-Speed Electric Shift Controlº or ªRear Axle,
Tw o
-Speed Airshift Controlº in the Index.
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2-11 Cold Weather Starting (Caterpillar

Diesel)
Because the diesel engine uses compression ignition, it
is harder to start in cold weather than a gasoline engine.
The air intake heater and use of the proper engine oil,
optional engine coolant heaters and optional ether
injection systems help cold weather starting. See the
Caterpillar

Operation & Maintenance Manual for
more information.
Diesel Engine Warm-Up
Several factors affect how quickly your diesel engine
warms up. These can include outside temperature,
engine load, idle time and your vehicle's option content.
Your vehicle may be equipped with some features that
can help the engine reach operating temperature sooner.
Some of these features are discussed below.
Also, remember that an automatic transmission adds
heat to the cooling system through the heat exchanger in
the radiator. Because of this, vehicles equipped with
automatic transmissions are often able to retain engine
coolant heat better than manual transmission vehicles.
See your Caterpillar

Operation & Maintenance manual
for additional diesel engine warm
-up information.
Engine Automatic Shutdown (If Equipped)
Your CHECK GAGES light will come on if the system
senses high engine temperature or low engine oil
pressure. If high engine temperature is detected, you
will also hear a tone alarm at two beats per second. The
alarm and the light will remain on until the condition is
fixed. If the engine temperature condition worsens, the
tone alarm will go to five beats per second. When a low
oil pressure condition is detected, the five beat per
second alarm will come on immediately.
If the system senses low engine coolant, the five beat
per second alarm and the LOW COOLANT warning
light will come on.
The five beats per second tone alarm means that your
engine will shut down in 25 seconds. Pull off the road
and shut off the engine. Don't start it until the reason for
the problem is known, and the problem is fixed. If the
engine shuts down when you are still in traffic, you can
restart the engine and get another 25 seconds of
operation. Do this only if you have to, since there is a
problem that can harm the engine if it isn't fixed.
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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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