PLATE 4875661 - Caterpillar

Probable Causes
Fuel quality
Quality of oil
Low engine temperature
Air intake and exhaust system
Reduced pressure of intake air
Excessive valve lash
Failure of the primary speed/timing sensorRecommended Actions
Fuel Quality
The quality of the fuel that is used in the engine will affect the rate of fuel consumption. Refer to "General Fuel Information" in the Operation and Maintenance Manual, "Refill Capacities".
If the fuel is not of an acceptable quality, drain the fuel system and replace the fuel filters. Refill the fuel system with fuel of an acceptable quality. Refer to the applicable sections in the Operation and Maintenance Manual.
If the fuel is of an acceptable quality, refer to "Quality of Oil".Quality of Oil
The nominal viscosity of the lubricating oil that is used in the engine will affect the rate of fuel consumption. The viscosity of lubricating oil is defined by the SAE grade of the lubricating oil. The grade of the lubricating oil must be correct for the ambient conditions. Lubricating oil that is intended for use in high ambient temperatures will have a negative effect upon the rate of fuel consumption in cold ambient temperatures. Refer to "Engine Oil" in the Operation and Maintenance Manual, "Refill Capacities".
The actual viscosity of the lubricating oil that is used in the engine will change throughout the service life of the oil. Lubricating oil that is heavily contaminated will have a negative effect upon the rate of fuel consumption.
If the oil is not of an acceptable quality or if the oil has exceeded the service life, drain the oil system and replace the oil filters. Refill the oil system with oil of an acceptable quality. Refer to the applicable sections in the Operation and Maintenance Manual.
If the oil is of an acceptable quality, refer to "Low Engine Temperature".Low Engine Temperature
The operating temperature of the engine will affect the rate of fuel consumption. Operation of the engine below the correct temperature will increase fuel consumption. Failure of the water temperature regulator can prevent the engine from operating at the correct temperature.
If the engine operating temperature is low, check the operation of the water temperature regulator. If the water temperature regulator does not operate correctly, a new water temperature regulator must be installed. Refer to Disassembly and Assembly, "Water Temperature Regulator - Remove and Install".Air Inlet and Exhaust System
Leakage of gas or an increased restriction in either the air intake or the exhaust system can reduce the flow of combustion gas through the engine. A change in the flow of combustion air into the engine adversely affects combustion efficiency and the rate of fuel consumption.
Check the air intake system for leakage or restrictions. Refer to Systems Operation, Testing and Adjusting, "Air Inlet and Exhaust System".
Check the exhaust system for leakage or restrictions. Refer to Systems Operation, Testing and Adjusting, "Air Inlet and Exhaust System".
Repair all defects. Verify that the repair has eliminated the fault.Reduced Pressure of Intake Air
If the pressure of the intake air at the intake manifold is lower than normal, either the speed of the engine will need