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To many, the diesel principle may not be new, however, the special features of Caterpillar Diesel Truck Engines require that the operator and the maintenance personnel become acquainted with the systems in order to give the engine the best possible care. Maximum service depends a great deal on a good maintenance schedule performed by reliable personnel with a basic understanding of the working principles and systems.Diesel Engine Principle
This diesel engine operates on the reciprocating piston 4-stroke cycle, compression ignition principle, and burns fuels commercially known as diesel fuels. The basic difference between the spark ignition engine and the diesel engine are; the method of introducing fuel into the system, and the method by which the fuel is ignited.The diesel engine always takes a full charge of "air only" on each inlet stroke, compresses it in an extremely small space causing the air to reach temperatures over 1000°F (537°C). Fuel is injected into the precombustion chamber as the piston nears the top of the compression stroke, where it mixes with the compressed air, and immediately starts to burn. This is called self-ignition, or spontaneous ignition. The expansion of the burning gases forces the piston down on a power stroke. Four Stroke Cycle Principle:
The four stroke cycle engine has separate strokes for each basic function. The four strokes and the order in which they occur are: Intake, compression, power and exhaust.It must be remembered that for the four stroke cycle to function, the inlet valves, exhaust valves, and fuel injection must be timed in proper sequence with the piston. This is accomplished by timing gears between the crankshaft, the valve train, and injection pumps. Intake Stroke: As the piston moves down on the inlet stroke the inlet valves are opened and exhaust valves are closed by the camshaft and rocker arm arrangement. Air is drawn in through the air cleaner by the turbocharger and forced through the water cooled aftercooler and then charges the cylinder through the intake valves. Compression Stroke: At the end of the intake stroke both inlet valves close and the exhaust valves remain closed. As the