CLAMP 9Y0047 - Caterpillar

Probable Causes
High inlet air temperature
Inlet air restriction
Air/fuel ratio
Excessive load
Incorrect base timing
Exhaust restriction
A buildup of deposits in the cylinder or internal oil leaksRecommended Repairs
Check the Inlet Air Temperature
High inlet air temperature can cause detonation. Check the inlet air temperature.Refer to Troubleshooting, "Inlet Air Temperature (High)".Inlet Air Restriction
Note: Inlet air restriction can cause uneven exhaust port temperatures. For example, the cylinders at the front half of the engine may have exhaust port temperatures that are 10 °C (50 °F) to 20 °C (68 °F) higher than the exhaust port temperatures for the cylinders at the rear half of the engine. If this occurs, measure the inlet air restriction for each turbocharger. Make repairs in order to equalize the inlet air restriction for both turbochargers.High inlet air restriction adversely affects engine performance. Refer to the applicable Gas Engine Technical Data Sheet for additional information.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.Air/Fuel Ratio
An air/fuel mixture that is too rich will increase the exhaust temperature. Verify that the exhaust emissions are correct. Refer to Systems Operation/Testing and Adjusting, "Air/Fuel Ratio Control - 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. Excessive Load
Make sure that the load is not excessive. Reduce the load. If necessary, disengage the driven equipment and test the engine.Check the Base Timing
Verify that the base timing is correct. Refer to Systems Operation/Testing and Adjusting, "Ignition Timing - Adjust".Measure the Exhaust Restriction
Measure the exhaust restriction during engine operation with a load. For data that is specific to the engine, refer to the Technical Marketing Information.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 leaksOther 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.