- High inlet air temperature
- Inlet air restriction
- Air/fuel ratio
- Excessive load
- Incorrect timing
- Exhaust restriction
- A buildup of deposits in the cylinder or internal oil leaks
Check the Inlet Air Temperature
High inlet air temperature can cause detonation. Check the inlet air temperature.
Refer to Troubleshooting, "Inlet Air Temperature Is Too High".
The maximum allowable inlet air restriction is 3.75 kPa (15 inches of H2O). If the indication is higher than the maximum permissible restriction, clean the filter element or install a new filter element. Check the restriction again. If the restriction remains too high, inspect the air inlet piping before the air cleaner for obstructions.
An air/fuel mixture that is too rich will increase the exhaust temperature. Verify that the exhaust emissions are correct. Refer to Operation and Maintenance Manual, "Carburetor Air/Fuel Ratio - Check/Adjust".
A change in the fuel energy content will change the air/fuel ratio. Obtain a fuel analysis.
The fuel supply pressure must be adequate and stable.
Make sure that the load is not excessive. Reduce the load. If necessary, disengage the driven equipment and test the engine.
Note: Data from a fuel analysis is required for this procedure.
Use the Digital Diagnostic Tool (DDT) or the Caterpillar Electronic Technician (ET) to check the ignition timing during engine operation with a load. Compare the timing to the recommended timing in the Engine Performance, "Fuel Usage Guide".
Adjust the ignition timing according to the recommended timing in the Engine Performance, "Fuel Usage Guide".
Measure the Exhaust Restriction
The maximum allowable exhaust restriction is 3 kPa (12 inches of H2O). Check for restriction in the exhaust system.
If the difference between the pressure at the exhaust elbow and the atmospheric pressure exceeds the specification, determine the cause. Make the necessary repairs.
Investigate the cause of the exhaust restriction. Perform adjustments and/or make repairs, as needed.
Check for Deposits in the Cylinder and Check for Internal Oil Leaks
Use a borescope to inspect the cylinders. Look for the following conditions:
- Deposits on the valve seats
- Deposits on the valve faces
- Deposits on the cylinder walls that are above the upper limit of the piston stroke
- Signs of internal oil leaks
Other signs of internal oil leaks include high oil consumption and blue smoke.
Note: Excessive deposits contribute to guttering of the valves.
If excessive deposits and/or signs of internal oil leaks are found, investigate the cause of the condition. Make repairs, as needed.