1999 GMC C-SERIES fuel

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6-71
Name Circuits Protected
CHAS Exhaust Brake, Air Suspension
Dump Valve, Air Dryer, HYD
ABS ECHU
PARK LP Auxiliary Wiring, Air Conditioner
Controls, Parking Lamps, Turn
Signals, Taillamps, Stoplamps,
Marker Lamps, Trailer Running
Lamps, Lighted Mirrors, Radio
Receiver, Mirror Clearance Lamps
HORN Horn/Diagnostic Connector
PRK BRK Parking Brake Module
FUEL Heated Fuel Filter (Diesel
Engines) or Fuel Pump
(Gasoline Engines)
AXLE Heated Mirrors, Radiator Shutters,
Tw o
-Speed Axle Motor,
Tw o
-Speed Axle Switch
MRKR LP Roof Marker Lamps,
Trailer Marker Lamps,
Marker Lamp RelayName Circuits Protected
CIG/AUX Cigarette Lighter,
Auxiliary Power Jacks
AUX Auxiliary Wiring Relay
IGN RLY/VIN Vehicle Interface Module
(Diesel Engines) or Generator,
Coil, Injectors (Gasoline Engines)
WDO Power Windows
CRNK Starter Relay
IGN SW Instrument Panel Cluster Telltales
AUX Auxiliary Wiring
RDO Radio, Auxiliary Wiring
DR LK Power Door Locks
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6-73
Name Circuits/Circuit Breakers
Protected
STP/HAZ
TURNStop Lamp, Turn Signal/Hazard
Lights, Fuel, Ignition Relay
(Gasoline Engines)
IGN SW3 Air Conditioner, Ignition Switch,
Axle, ChassisName Circuits/Circuit Breakers
Protected
INT/EXT
LIGHTSParking Lamps,
Dome/Panel Lights
HEAD LAMP Headlamps,
Daytime Running Lamps
AUX WRG Auxiliary, Park Brake
IGN SW1 Ignition Switch, Wash/Wipe,
Crank, Radio
HYD PUMP Hydraulic Brake,
Brake Pump Motor
HYD ABS EHCU
PWR
WDO/LCKSWindow, Door Locks
PARK BRK Parking Brake Motor
BLOWER
HORNBlower, Horn, Cigarette
Lighter/Auxiliary
FUEL/ENGINE Empty
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6-74
Replacement Bulbs
It is recommended that you use an AC
type bulb
whenever you need to replace one.
Before you replace any bulbs, be sure that all lamps are
off and the engine isn't running.
Capacities and Specifications
Replacement part numbers listed in this section are
based on the latest information available at the time of
printing. They are subject to later change. If a part listed
here isn't the same as the part in your vehicle when it
was built, or if you have any questions, please contact
your GM Truck dealer.
Engine Identification and Data
Engine RPO LG5 LP4/L21
Engine Type 7.2L L6 7.4L V8
Fuel System HEUI SPFI
Firing Order
1
-5-3-6-2-41-8-4-3-6-5-7-2
Wheel Nut Torque
Refer to ªTightening the Wheel Nutsº in this section for
wheel nut torque information.
Cooling System Capacity
Model Quarts (Liters)
7.2L 32.0 (30.0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
with automatic transmission 30.0 (28.4). . . . . . . . . .
7.4L 25.0 (23.7). . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
with automatic transmission 23.0 (22.7). . . . . . . . . .
Above capacities (volumes) are approximate.
Crankcase Capacity
Capacities (volumes) shown are for normal refill. Add
oil as indicated when the oil filter element is changed.
Capacities given are approximate
-- keep level within
the operating range. Do not operate with fluid level
below the ADD line.
Engine
Capacity
-- Quarts (Liters)
7.2L 21 (19.0)*
7.4L 8 (7.5)
*Additional oil is required with auxiliary oil filter
systems. Make sure to add enough extra oil to fill the
auxiliary oil filter system. For vehicles equipped with
the LUBERFINER 750
-C, add 14 quarts (13.25 L).
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6-76 Rear Axle Lubricant Capacity
Single Speed Axle Lubricant, Pints (Liters)
15040S 21.0 (10.1). . . . . . . . . . . . . . . . . . . . . . . . . . . .
19060S 28.0 (12.8). . . . . . . . . . . . . . . . . . . . . . . . . . . .
21060D 28.0 (14.7). . . . . . . . . . . . . . . . . . . . . . . . . . . .
21060S 28.0 (14.7). . . . . . . . . . . . . . . . . . . . . . . . . . . .
22060S 28.0 (14.7). . . . . . . . . . . . . . . . . . . . . . . . . . . .
22080S 40.0 (20.3). . . . . . . . . . . . . . . . . . . . . . . . . . . .
23080S 40.0 (20.3). . . . . . . . . . . . . . . . . . . . . . . . . . . .
23431 40.0 (20.3). . . . . . . . . . . . . . . . . . . . . . . . . . . . .
23105S 48.0 (22.7). . . . . . . . . . . . . . . . . . . . . . . . . . . .
26085P 41.0 (19.5). . . . . . . . . . . . . . . . . . . . . . . . . . . .
26105S 48.0 (22.7). . . . . . . . . . . . . . . . . . . . . . . . . . . .
30105S 46.0 (23.2). . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tw o
-Speed Axle Lubricant, Pints (Liters)
15040T 24.0 (11.5). . . . . . . . . . . . . . . . . . . . . . . . . . . .
19060T 35.0 (17.5). . . . . . . . . . . . . . . . . . . . . . . . . . . .
21060T 35.0 (17.5). . . . . . . . . . . . . . . . . . . . . . . . . . . .
22060T 35.0 (17.5). . . . . . . . . . . . . . . . . . . . . . . . . . . .
23080T 39.0 (19.9). . . . . . . . . . . . . . . . . . . . . . . . . . . .
26080T 41.0 (19.5). . . . . . . . . . . . . . . . . . . . . . . . . . . .
Above capacities (volumes) are approximate.Tandem Axles Lubricant, Pints (Liters)
DS344 (front) 29.0 (15.1). . . . . . . . . . . . . . . . . . . . . . .
RS344 (rear) 28.0 (13.2). . . . . . . . . . . . . . . . . . . . . . . .
DS454 (front) 29.0 (15.1). . . . . . . . . . . . . . . . . . . . . . .
RS454 (rear) 28.0 (13.2). . . . . . . . . . . . . . . . . . . . . . . .
DS404, DS404P (front) 29.0 (15.1). . . . . . . . . . . . . . .
RS404 (rear) 34.0 (16.1). . . . . . . . . . . . . . . . . . . . . . . .
DT402P (front) 34.0 (16.1). . . . . . . . . . . . . . . . . . . . .
RT402 (rear) 34.0 (16.1). . . . . . . . . . . . . . . . . . . . . . . .
Above capacities (volumes) are approximate.
Fuel Tank Capacity
Model Gallons (Liters)
Standard 50 (189.0). . . . . . . . . . . . . . . . . . . . . . . . . . .
Optional 35 (132.5). . . . . . . . . . . . . . . . . . . . . . . . . . .
Optional 60 (227.1). . . . . . . . . . . . . . . . . . . . . . . . . . .
Optional* 70 (264.0). . . . . . . . . . . . . . . . . . . . . . . . . .
Optional** 100 (378.0). . . . . . . . . . . . . . . . . . . . . . . .
* Two 35
-gallon (132 L) tanks
**Two 50
-gallon (189 L) tanks
Above capacities (volumes) are approximate.
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6-77
Air Conditioning Refrigerants
Not all air conditioning refrigerants are the same.
If the air conditioning system in your vehicle needs
refrigerant, be sure the proper refrigerant is used.
If you're not sure, ask your dealer.
Air Conditioning Refrigerant Capacity
Refrigerant R-134a 2.5 lbs. (1.134 kg). . . . . . . . . . . .
This capacity (volume) is approximate.
Normal Maintenance Replacement
Parts
Allison Transmission External Filters
Engine GM (AC) Part Number
7.2L 25011122 (PF897). . . . . . . . . . . . . . . . . . . . . . .
7.4L 25011122 (PF897). . . . . . . . . . . . . . . . . . . . . . .
Air Compressor Filter
Air Compressor GM Part Number
Bendix Tu
-Flo
550 (13.2 CFM)2467368
Service Replacement Part and
Filter Recommendations
Engine 7.2L 7.4L
RPO LG5 LP4/L21
Spark Plug Ð AC Type R41
-932
ÐGap Ð 0.060 inch
(1.52 mm)
ÐTorque Ð 22.0 lb. ft.
(30.0 Nm)
Oil Filter CAT

2P4004 AC Type PF-932
PCV Valve Ð AC Type CV
-774C
Air Cleaner* Donaldson
P522606Donaldson
P533355
Fuel Filter AC
-TP-915 Pri-
mary**AC Type GF-481
Pressure Caps RC
-54 Ð
*Optional Davco (K28) D350921 spin
-on type filter
located in component box.
**Optional Cold Weather (KUK) Racor B6484GM
spin
-on type located in component box. Optional Davco
heated fuel water separator mounted on the side of the
diesel engine.
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7-4
Part A: Scheduled Maintenance
Services
Using Your Maintenance Schedule
We at General Motors want to help you keep your
vehicle in good working condition. But we don't know
exactly how you'll drive it. You may drive very short
distances only a few times a week. Or you may drive
long distances all the time in very hot, dusty weather.
You may use your vehicle in making deliveries or in
many other ways.
Because of all the different ways people use their
vehicles, maintenance needs vary. You may need more
frequent checks and replacements. So please read the
following and note how you drive. If you have any
questions on how to keep your vehicle in good
condition, see your GM dealer.
This part tells you the maintenance services you should
have done and when you should schedule them. If you
go to your dealer for your service needs, you'll know
that GM
-trained and supported service people will
perform the work using genuine GM parts.The proper fluids and lubricants to use are listed in Part C.
Make sure whoever services your vehicle uses these. All
parts should be replaced and all necessary repairs done
before you or anyone else drives the vehicle.
This schedule is for vehicles that:

carry passengers and cargo within recommended
limits. You will find these limits on your vehicle's
Certification/Tire label. See ªLoading Your Vehicleº
in the Index.

are driven on reasonable road surfaces within legal
driving limits.

use the recommended fuel. See ªFuelº in the Index.
Scheduled Maintenance Supplements
If your vehicle has a Caterpillar diesel engine, your
GM Owner's Manual is supplemented by the Caterpillar
Diesel Engine Operation & Maintenance Manual. If your
vehicle has an Allison transmission, your GM Owner's
Manual is supplemented by an Allison Transmission
Operator's Manual. Always refer to these manuals for
related maintenance services.
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7-8 24,000 Miles (40 000 km) (Continued)

Evaporative Control System service (if equipped) (or
every 24 months, whichever occurs first). (3)(26)

Rear axle air shift motor service. (11)
Check air brake relay valve operation and check for
leaks (or every month, or every 300 hours,
whichever occurs first).
Air brake chamber service (or every 2 months,
whichever occurs first). (41)
Trailer brake hand control valve service (or every
3 months, or 900 hours, whichever occurs first). (42)
27,000 Miles (45 000 km)
Engine oil and filter service. (3)(9)
Check fluid levels (or every 3 months, whichever
occurs first). (1)(2)(6)
30,000 Miles (50 000 km)
Engine oil and filter service. (3)(9)
Check fluid levels (or every 3 months, whichever
occurs first). (1)(2)(6)
Chassis lubrication service (or every 6 months,
whichever occurs first). (12)
Replace fuel filter(s) (or every 12 months, whichever
occurs first). (3)Air cleaner filter replacement service (or every
24 months, whichever occurs first). (3)(4)(27)
Steering system service. (13)
Front and rear suspension service. (14)
Spring
-to-axle U-bolts and shackle bolts service. (16)
Exhaust system service (or every 6 months,
whichever occurs first). (3)(4)(17)
Air brake service (or every 6 months, whichever
occurs first). (39)
Lubricate door hinge pins and rollers with engine oil.
Wheels and tires service. (15)
Hydraulic brake service (or every 6 months,
whichever occurs first). (7)
Hydraulic parking brake service (or every 6 months,
whichever occurs first). (8)
Clutch pedal free travel service. (10)
Air brake automatic slack adjuster service (or every
500 hours, whichever occurs first). (40)
33,000 Miles (55 000 km)
Engine oil and filter service. (3)(9)
Check fluid levels (or every 3 months, whichever
occurs first). (1)(2)(6)
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7-11 51,000 Miles (85 000 km)

Engine oil and filter service. (3)(9)

Check fluid levels (or every 3 months, whichever
occurs first). (1)(2)(6)
54,000 Miles (90 000 km)

Engine oil and filter service. (3)(9)

Check fluid levels (or every 3 months, whichever
occurs first). (1)(2)(6)

Chassis lubrication service (or every 6 months,
whichever occurs first). (12)

Inspect door hinge pins and bushings and replace if
necessary. Lubricate door hinge pins and rollers with
engine oil.

Replace air conditioning filter dryer (or every
18 months, whichever occurs first, and whenever
refrigerant charge is lost for any reason).

Wheels and tires service. (15)

Hydraulic brake service (or every 6 months,
whichever occurs first). (7)

Hydraulic brake caliper service (or every 6 months,
whichever occurs first). (22)

Hydraulic parking brake service (or every 6 months,
whichever occurs first). (8)

Clutch pedal free travel service. (10)
Spark plug service. (3)(28)

Clean air brake application valve (or every 3 months,
or every 300 hours, whichever occurs first);
lubricate linkage.
57,000 Miles (95 000 km)

Engine oil and filter service. (3)(9)

Check fluid levels (or every 3 months, whichever
occurs first). (1)(2)(6)
60,000 Miles (100 000 km)

Engine oil and filter service. (3)(9)

Check fluid levels (or every 3 months, whichever
occurs first). (1)(2)(6)

Chassis lubrication service (or every 6 months,
whichever occurs first). (12)

Replace fuel filter(s) (or every 12 months, whichever
occurs first). (3)

Air cleaner filter replacement service (or every
24 months, whichever occurs first). (3)(4)(27)

Steering system service. (13)

Front and rear suspension service. (14)

Spring
-to-axle U-bolts and shackle bolts service. (16)
(Continued)
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