* The Diesel engine fuel system consists of:
* An engine-mounted secondary fuel filter.
* Frame-mounted Horizontal Fuel Conditioner Module (HFCM).
* A unit injector for each cylinder.
The HFCM acts as a primary fuel filter/water separator which removes both water and impurities from the fuel. The engine-mounted fuel filter and the HFCM filter should be changed at the recommended service interval. Refer to the Scheduled maintenance guide section of this manual for more information.
The HFCM should be drained at regular intervals or when the WATER IN FUEL 
light illuminates in the instrument cluster.
The fuel injectors are located in the center of the combustion chambers in the cylinder head between the rocker arm assemblies. The glow plug system and fuel injection system are controlled through the Powertrain Control Module (PCM) and Fuel Injection Control Module (FICM) .
Fuel is drawn from the fuel tank by a frame-mounted electric fuel pump. The fuel pump provides pressurized fuel to the engine and is electronically controlled by the fuel pump PCM relay. The fuel pump contains a pressure relief valve for overpressure protection in the event of restricted flow.
It is important to change the engine oil at the recommended service intervals, because oil viscosity is important in maintaining the oil pressure required to actuate the fuel injectors. Extended oil change intervals can negatively affect engine performance, fuel economy and engine life. Refer to the engine oil specification chart located under Engine oil specifications in the General maintenance information chapter.
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The glow plug system consists of:
Eight glow plugs.
The glow plug control module (GPCM).
Engine oil temperature (EOT) sensor.
Barometric pressure (BARO) sensor.
The glow plug system is electronically controlled by the PCM. The GPCM energizes the glow plugs
immediately after the ignition is placed in the ON position, then determines how long the glow plugs will be on according to the EOT and BARO sensors. The required time for the glow plugs to be energized decreases as the engine oil temperature and barometric pressure increase.
The cooling system contains an engine oil cooler which is mounted in the center valley of the engine. The cooler's function is to regulate engine oil temperature.
Engine governed speed
The engine governor is controlled by the PCM. The PCM controls fuel input to limit maximum engine speed. It will not, however, prevent engine overspeeding resulting from downshifting at high vehicle speed or by descending steep grades at too high a vehicle speed for the selected transmission gear. For maximum vehicle speed in various gears, refer to Manual transmission shift speeds in the Driving tips chapter. Do not exceed 3,600 rpm. Maximum engine governed speed is 4,000 rpm depending on engine load. Excessive rpm can only be achieved by manually downshifting at too high of a vehicle speed.
Operating the engine beyond the governed speed can cause severe engine damage.
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The restriction gauge, located on the upper housing of the air cleaner assembly, monitors the condition of the air filter element in two ways:
First, the colored indictor inside the gauge highlights the percentage that the air filter element is clogged with dust or contaminants. Refer to Engine Compartment in Service Points chapter.
Second, the gauge contains an electrical switch which illuminates a warning light on the instrument cluster when the air filter element is 100% clogged. Refer to Engine Air Filter Warning Light.
Check the air filter restriction gauge whenever the hood is raised to perform general engine maintenance. If the vehicle is operated in extremely dusty conditions, check the gauge at least every 800 km (500 miles), or two weeks, whichever comes first.
The air filter element must be replaced when the colored band on the gauge reaches the CHANGE FILTER mark. Engine performance and fuel economy are adversely affected when the maximum restriction is reached.
Blowing-out the air filter element with compressed air is not recommended as the compressed air may damage the filter paper.
Note: It is not possible to determine the level of filter clogging by visual appearance alone. A filter which appears to be dirty may actually have several thousand kilometers (miles) of life remaining.
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After servicing the air filter element, reset the restriction gauge by pressing the button on the end of the gauge.
Note: If the vehicle is operated in a heavy snow storm, in blowing snow or the vehicle is equipped with a snowplow, the engine air filter element may become partially clogged with snow and/or ice. If this occurs, the air filter restriction gauge will move to the CHANGE FILTER mark and the engine may experience a significant reduction in power output. The vehicle may be driven under these conditions for up to 400 km (250 miles) without damage to the engine or related components.
At the earliest opportunity, clear all snow and ice from the air induction system and replace the air filter element, or remove the element and dry it out. Reset the restriction gauge by pressing the button on the end of the gauge. The air filter warning light on the instrument cluster may be used, in addition to the underhood restriction gauge, to monitor the condition of the air filter element. Refer to the Warning lights chapter.
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If your vehicle is equipped with an automatic transmission, ensure the gearshift lever is ill P (Park) and the parking brake is set before you turn the key. Do not press the accelerator during starting.
COLD WEATHER STARTING Do not crank the engine for more than 30 seconds at a time as starter damage may occur. If the engine fails to start, turn the key to OFF and wait 30 seconds before trying agam.
Note: Do not add gasoline, gasohol or alcohol to Diesel fuel. This practice creates a serious fire hazard and causes engine performance problems.
1. Make sure all vehicle occupants have buckled their safety belts. For more information on safety belts and their proper usage, refer to Seating and safety restraints chapter ill the owner guide.
2. Make sure the headlamps and vehicle accessories are off.
3. Turn the key to the ON position. When the WAIT TO START light goes off, turn the key to START. (For Canadian vehicles, the daytime running lamps will be on if the parking brake is not applied and the key is turned to ON.)
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Page Last Updated: Feb. 5, 2004