Probable Causes
- Excessive load
- Poor fuel quality
- Plugged fuel filter or plugged air filter
- Excessive engine oil
- High fuel temperature
- Air inlet leak after the turbocharger
- Exhaust leak before the turbocharger
- Air inlet restriction or exhaust restriction
- High air inlet temperature
- Fuel ratio control setting
- Binding in the fuel injection control linkage
- Damage to the valve train or damage to the unit injectors
- Improper fuel injection timing
- Incorrect valve adjustment
- Incorrect fuel setting
- Faulty turbocharger
- Low fuel pressure
- Air in fuel
- Faulty unit injector
- Low cylinder compression
Recommended Repairs
Excessive Load
Ensure that the engine is not operating under an excessive load. Excessive load can be caused by any of the following conditions:
- High altitude operation
- Low tire pressure
- Parasitic loads
Poor Fuel Quality
Ensure that the vent for the fuel tank is not plugged. Ensure that there is good, clean fuel in the tank. When possible, interview the operator in order to determine if fuel quality is in question. Refer to Troubleshooting, "Fuel Quality".
Plugged Fuel Filter or Plugged Air Filter
Inspect the air filter. Replace the air filter, if necessary. Check the water separator (if equipped). If the fuel filter has not been replaced recently, replace the fuel filter.
Excessive Engine Oil
Check the engine oil level. If the engine oil level is high, drain the oil. Refill the system to the correct level. Determine the source of the extra oil. If the oil is diluted with fuel, locate the fuel leak and repair the fuel leak. Refer to Troubleshooting, "Fuel In Engine Oil".
High Fuel Temperature
Verify that the temperature of the fuel in the fuel tank is less than 78 °C (172°F). A low fuel level in the fuel tank can cause high fuel temperature. Check for proper operation of the fuel heater, if equipped.
Air Inlet Leak After the Turbocharger
Check for loose connections between the turbocharger and the inlet manifold. A small air leak can cause problems when the engine is operating under full load. Check the aftercooler for visible signs of leaking. A soap solution can be used to detect leaks. Allow the engine to cool before the soap solution is used.
Exhaust Leak Before the Turbocharger
Exhaust leaks between the exhaust manifold and the turbocharger can reduce boost pressure. Check for exhaust leaks at the exhaust manifold. Also check for exhaust leaks at the mounting flange for the turbocharger.
Air Inlet Restriction or Exhaust Restriction
Measure the air inlet restriction and measure the exhaust system restriction. Refer to Systems Operation, Testing And Adjusting. Measure the air inlet restriction at the inlet of the turbocharger. The maximum inlet restriction is 6.2 kPa (25 inches of H2O). Measure the exhaust restriction after the turbocharger. The maximum exhaust restriction is 10 kPa (40 inches of H2O). Refer to Technical Marketing Information (TMI) for additional data.
High Air Inlet Temperature
Check for proper operation of the air inlet heater (if equipped). Measure the inlet air temperature. Compare the inlet air temperature to the specification for the inlet air temperature that is listed in the TMI. If the inlet air temperature is high, check the aftercooler for restrictions and also check the aftercooler for proper operation.
Fuel Ratio Control Setting
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To avoid personal injury, always wear eye and face protection when using pressurized air. |
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Stop the engine. Remove the control line that connects the FRC to the inlet manifold. Apply 140 kPa (20 psi) to 200 kPa (29 psi) air pressure to the FRC. Listen for air leakage in the governor. If leaking air is detected, replace the FRC. Check the setting for the FRC. Refer to Service Manual, SENR6454, "3114, 3116 & 3126 Engine Governors".
Binding in the Fuel Injection Control Linkage
If the fuel injection control linkage is binding, refer to Troubleshooting, "Fuel Injection Control Linkage".
Damage to the Valve Train or Damage to the Unit Injectors
Remove the valve cover. Inspect the following items for damage:
- Unit injectors
- Push rods
- Rocker arms
Refer to Troubleshooting, "Unit Injector".
Improper Fuel Injection Timing
Check the fuel injection timing. Refer to Systems Operation, Testing And Adjusting, "Fuel Timing".
Incorrect Valve Adjustment
Check the valve adjustment. Refer to Systems Operation, Testing And Adjusting, "Valve Lash".
Incorrect Fuel Setting
Check the fuel setting. Refer to Systems Operation, Testing And Adjusting, "Fuel Setting".
Faulty Turbocharger
Inspect the turbocharger compressor wheel. If excessive deposits are found on the compressor wheel or the compressor wheel is damaged, determine the cause. If the cause is not found, the problem will reoccur. Rotate the compressor wheel in order to check for dragging or binding. Check for excessive play in bearings.
Low Fuel Pressure
Check the fuel pressure. Refer to Systems Operation, Testing And Adjusting. Minimum fuel pressure with clean fuel filters is 50 kPa (7.3 psi) at low idle or 200 kPa (29 psi) at high idle. If the fuel pressure is low, make sure that the fuel filters are not plugged. Premature plugging of the fuel filter indicates excessive fuel system contamination. Ensure that the fuel system is clean. Refer to Troubleshooting, "Fuel Transfer Pump".
Air in the Fuel
Refer to Troubleshooting, "Air In Fuel".
Faulty Unit Injector
Use the 1U-6661 Pop Tester Group to check the unit injectors for proper operation. Refer to Special Instruction, SEHS9787. Use the go/no-go gauge to check the unit injector height. Check the injectors for external leakage.
Low Cylinder Compression
Check for signs of broken piston rings, faulty cylinder head gasket, and worn cylinders or valves. If the engine runs properly and there is not excessive blowby or excessive oil consumption, the cylinder compression is probably acceptable.