Working principle of diesel engine

In diesel engines, clean air is sucked into the cylinders and highly compressed there. As a result, the temperature in the cylinders rises above the temperature of the diesel fuel. If the piston is in front of TDC, then diesel fuel is injected into highly compressed and heated to almost 600°C air and ignites there. Spark plugs are not required.

With a very cold engine, it may happen that the ignition temperature is not reached as a result of compression. In this case, you must first warm up the engine. For this purpose, a glow plug is located in each swirl chamber, which heats the combustion chamber. In addition, the diesel engine contains an element of expanding material that moves to the position "earlier" injection regulator piston in the high pressure fuel pump. As a result, fuel is injected into hot air earlier and a cold engine starts faster. Once the engine has reached its operating temperature, the expanding material element automatically returns to its original position.

Fuel is sucked in by the high pressure fuel distribution pump from the fuel tank. A high pressure of approximately 150 bar is created in the fuel pump to inject diesel fuel and the fuel is distributed according to the ignition sequence to the individual cylinders. At the same time, the regulator in the high pressure fuel pump adjusts the amount of fuel injected according to the position of the gas pedal. Through the jets, diesel fuel is injected at the right time into the prechamber of the corresponding cylinder. Due to the shape of the pre- and vortex chamber, the sucked-in air acquires a certain vortex motion during the compression process, as a result of which the injected fuel is optimally mixed with the air.


Before entering the high pressure fuel pump, the fuel passes through the fuel filter. The filter filters out dirt and water. Therefore, it is extremely important to dehydrate and change the fuel filter according to the maintenance instructions.

The high pressure fuel pump is maintenance free. All moving parts of the pump are lubricated with diesel fuel. The fuel pump is driven by the crankshaft through a separate toothed belt.

Since the diesel engine in which self-ignition occurs is not switched off by the ignition voltage cut-off device, it is equipped with a solenoid valve. As a result of turning off the ignition, the power supply to the solenoid valve is cut off, the valve closes the fuel channel, and the engine is turned off. When the engine is started, voltage is again applied to the solenoid valve and the valve opens the fuel passage again.