- Excessive load
- Fuel system leaks
- Fuel quality
- Air inlet restriction
- Exhaust restriction
- Incorrect fuel injection timing
- Faulty automatic timing advance
- Incorrect valve adjustment
- High fuel setting
- Faulty fuel ratio control
- Faulty fuel injection nozzle
- Faulty turbocharger
Ensure that the engine is not operating under an excessive load. Excessive load can be caused by any of the following items:
- High altitude operation
- Low tire pressure
- Parasitic loads
Inspect the fuel system for leaks. Check all lines, hoses, and fittings for leaks. Tighten any loose connections. Check for the presence of fuel in the lubricating oil.
Check the API of the fuel. Refer to Troubleshooting, "Fuel Quality".
Measure air inlet restriction. Refer to Systems Operation, Testing And Adjusting, "Restriction Of Air Inlet And Exhaust". Check the air flow with a water manometer or a vacuum gauge. Connect the gauge to the engine air inlet between the air cleaner and the inlet to the turbocharger. Check the air flow with the engine at full load rpm. The maximum allowable air inlet restriction is 6.25 kPa (25 inches of H2O).
Inspect the exhaust system. Refer to Systems Operation, Testing And Adjusting, "Restriction Of Air Inlet And Exhaust". Check for damage to piping or for a faulty muffler. If no damage is found, check the exhaust system for back pressure from the exhaust (pressure difference measurement between exhaust outlet and atmosphere). The maximum exhaust restriction is 10 kPa (40 inches of H2O). Refer to Technical Marketing Information (TMI) for additional data.
Incorrect Fuel Injection Timing
Ensure that the fuel injection timing is correct. Make necessary adjustments. Refer to Systems Operation, Testing and Adjusting, "3406C Diesel Truck Engine".
Faulty Automatic Timing Advance
Check the automatic timing advance for proper operation. Refer to Systems Operation, Testing and Adjusting, "3406C Diesel Truck Engine".
Check the valve adjustment. Refer to Systems Operation, Testing and Adjusting, "Valve Lash Setting".
Ensure that the fuel setting is correct. Make necessary adjustments. Refer to Systems Operation, Testing and Adjusting, "Fuel Setting Procedure".
Check the operation of the fuel ratio control. Refer to Systems Operation, Testing and Adjusting, "3406C Diesel Truck Engine".
Faulty fuel injection nozzles can cause the engine to misfire, which will cause the engine to run rough. Faulty fuel injection nozzles can also cause too much smoke even if the engine is running smoothly. Check the fuel injection nozzles. Refer to Special Instruction, SEHS7292 for additional information.
Check the inlet manifold and the exhaust manifold for oil. If oil is present in the inlet manifold or the exhaust manifold, repair the turbocharger or replace the turbocharger.