COUPLING AS- 2632631 - Caterpillar

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 compressionRecommended 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 loadsPoor 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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