When a diesel engine is running, clean air is sucked into its cylinders, which is compressed to high pressure. In this case, the air temperature rises above the ignition temperature of diesel fuel. Fuel is injected into the cylinder with some advance and ignites spontaneously. Thus, spark plugs are not used to ignite the fuel in a diesel engine.
On a cold engine, the temperature of the compressed air may not reach the required value for ignition. In this case, additional preheating is required. For this purpose, a glow plug is installed in each cylinder, which heats the combustion chamber. The duration of heating depends on the ambient temperature and is regulated by the engine control unit and the preheating relay.
Before entering the injection pump, the fuel is cleaned of contaminants and water in the fuel filter. Therefore, it is important to remove water from the fuel filter or replace it in accordance with the requirements of the maintenance schedule (see chapter Vehicle settings and routine maintenance).
Turbocharging is used to increase power on some engines.
Diesel engines are controlled by an electronic system similar to that of gasoline engines (see Section Power supply system for gasoline engines).