The reasons for diesel entering the oil pan of Cummins NT855 diesel engine

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(1) The manual shut-off valve of the fuel tank failed or was forgotten to close, causing diesel to flow into the fuel injector by itself through the float fuel tank and PT fuel pump when the machine was shut down, and then seep into the oil pan through the combustion chamber.

(2) The oil seal of the main shaft of the PT fuel pump is damaged, causing diesel to pass through this oil seal and enter the oil pan via the timing gearbox.

(3) The sealing ring of the electromagnetic shut-off valve of the PT fuel pump failed. Diesel fuel flowed into the injector by itself through the shut-off valve and seeped into the oil pan through the combustion chamber.

(4) When the fuel injector's nozzle is too large (the normal value is approximately 0.2032mm) or damaged, fuel drips into the combustion chamber when the machine is shut down and then seeps into the oil pan.

(5) The O-rings on the upper and lower parts of the fuel injector failed. The fuel entered the valve chamber and combustion chamber through the seals and then seeped into the oil pan.

(6) The fuel injection timing of the fuel injector is incorrect, resulting in incomplete combustion, and the excess diesel flows along the cylinder wall into the oil pan.

(7) Carbon deposits at the fuel injector, or severe wear or jamming of the fuel injector pair, cause poor atomization, resulting in fuel dripping. Incompletely burned diesel then flows along the cylinder wall into the oil pan.

(8) If the float valve or conical valve in the float oil tank fails, diesel will seep into the oil pan through the injector from the float oil tank when the machine is shut down.

(9) The one-way check valve on the return manifold of the PT fuel system failed, and the diesel from the float tank flowed to the injector by itself and then seeped into the oil pan.

(10) Severe wear of the piston, piston rings and cylinder liner leads to poor engine operation and incomplete combustion, causing excess diesel to flow along the cylinder wall into the oil pan.

(11) Some individual cylinders fail to operate due to too low pressure, causing diesel to flow into the oil pan.

(12) Clogging of the air filter or damage to the exhaust gas turbocharger, etc., can cause insufficient air intake and incomplete combustion in the diesel engine, resulting in diesel flowing along the cylinder wall into the oil pan.