Fuel Knock/Combustion Noise

DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with throttle opening.

PRELIMINARY CHECKS

^ Refer to Important Preliminary Checks. Testing and Inspection
^ Make sure the customer has an actual problem.
^ Check the fuel quality. Refer to Fuel Systems. Testing and Inspection

COOLING SYSTEM CHECKS

^ Check for obvious overheating problems. Refer to Engine Cooling.
^ Check for a low engine coolant level.
^ Check for a loose water pump belt.
^ Check for restricted air flow through the radiator, or restricted coolant flow.
^ Check for a faulty or incorrect thermostat.
^ Check for a correct coolant solution. The solution should be a 50/50 mix of antifreeze and water.

SENSOR CHECK

^ Check the Engine Coolant Temperature (ECT) sensor using the scan tool to compare the engine coolant temperature with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5° greater or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit or the sensor itself.

FUEL SYSTEM CHECKS

^ Check for air leaks in fuel supply to injection pump. Refer to Fuel System Check. Diesel MFI Pump
^ Check the injection pump static timing. Refer to Checking/Adjust Injection Timing. Adjustments

ENGINE MECHANICAL CHECKS

^ Check for incorrect basic engine parts such as cam, heads, pistons, etc.
^ Check for excessive oil entering combustion chamber.

ADDITIONAL CHECKS

^ Check the Service Bulletins for control module software updates.