STUD AS 1378460 - Caterpillar

Probable Causes
Diagnostic codes
Misreading of fuel level
Fuel leakage
Fuel quality
Quality of oil
Coolant temperature
Prolonged operation at idle speed
Air intake and exhaust system
Cooling fan
Reduced pressure of intake air
Excessive valve lash
Failure of the primary speed/timing sensorRecommended Actions
Note: The procedures have been listed in order of probability. Complete the procedures in order.
Table 1
Troubleshooting Test Steps Values Results
1. Diagnostic Codes
Note: Certain diagnostic codes and/or event codes may cause high fuel consumption.
A. Download the Warranty Report and the Product Status Report with Histograms before performing any troubleshooting or clearing any diagnostic codes.
Note: The downloaded information will be required by the Dealer Solutions Network (DSN) if troubleshooting assistance is needed.
B. Use the electronic service tool to check for active or logged codes.
Diagnostic codes
Result: A diagnostic code is present.
Repair: Troubleshoot the code and then verify that the fuel consumption is normal.
Result: A diagnostic code is not present.
Proceed to Test Step 2.
2. Misreading of Fuel Level
Note: Misreading of the fuel gauge can give a false indication of fuel consumption.
A. Monitor the fuel consumption over a period of 50 engine hours.
Fuel level
Result: Fuel consumption is normal for the operating conditions.
Return the unit to service.
Result: Fuel consumption is high for the operating conditions.
Proceed to Test Step 3.
3. Fuel Leakage
A. Check the engine for signs of fuel leakage.
Fuel leaks
Result: Evidence of a fuel leak is found.
Repair: Repair or replace the component that is leaking fuel.
Result: No evidence of a fuel leak is found.
Proceed to Test Step 4.
4. Fuel Quality
Note: The grade of the fuel affects the rate of fuel consumption. Refer to the engines Operation and Maintenance Manual for additional information.
Cold weather adversely affects the characteristics of the fuel. Refer to the Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold-weather operation.
A. Check the fuel quality. Refer to Systems Operation, Testing, and Adjusting, "Fuel Quality - Test".
B. Refer to Operation and Maintenance Manual for information on the proper characteristics of the fuel for the engine.
Fuel quality
Result: The fuel quality does not meet specifications.
Repair: Drain the fuel system and replace the fuel filters. Refer to the Operation and Maintenance Manual, "Fuel System Primary Filter (Water Separator) Element - Replace" and Operation and Maintenance Manual, "Fuel System Filter - Replace".
Fill the fuel system with fuel that meets the standard in the Operation and Maintenance Manual, "Fluid Recommendations".
Prime the fuel system. Refer to the Operation and Maintenance Manual, "Fuel System - Prime".
Result: The fuel quality meets specifications.
Proceed to Test Step 5.
5. Quality of Oil
Note: 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 for high ambient temperatures will affect fuel consumption in cold ambient temperatures.
A. Check that the engine oil meets the required specification. Refer to "Engine Oil" in the Operation and Maintenance Manual, "Refill Capacities".
Engine oil quality
Result: The engine oil does not meet the required specification.
Repair: Drain