In a very cold engine, it may be that the ignition temperature of the diesel fuel is not reached when the air is compressed. In this case, the engine must be preheated. For this purpose, each swirl chamber has a glow plug that heats the combustion chamber. In addition, the diesel engine has a thermostat (with solid filler), which moves the piston of the injection timing regulator on the high-pressure fuel pump in the advance direction via a cable in the casing. Due to this, the fuel is injected into the hot air earlier and the cold engine starts faster. When the engine reaches its operating temperature, the thermostat element automatically returns back.
Fuel is sucked from the fuel tank by the distribution fuel injection pump. The fuel injection pump creates the necessary high pressure for injecting diesel fuel (about 130 bar), and the fuel is distributed among the individual cylinders in accordance with their operating order. At the same time, the regulator in the high-pressure fuel pump controls the amount of injected fuel in accordance with the position of the gas pedal. Through the nozzle, diesel fuel is injected at the right moment into the prechamber of the corresponding cylinder. Due to the shape of the prechamber or swirl chamber, the sucked air during the compression stroke acquires a swirl-like motion, i.e. the injected fuel is mixed with air in an optimal way.
Before the fuel gets to the injection pump, it passes through the fuel filter. There, impurities and water are separated. Therefore, it is very important that the fuel filter is replaced or drained of water at the required frequency.
The fuel injection pump is not serviced. All moving parts of the fuel injection pump are lubricated with diesel fuel. The fuel injection pump is driven from the crankshaft by a separate toothed belt.
Since the diesel is a self-ignition engine, it cannot be turned off by disconnecting the voltage from the ignition system, and it has a solenoid valve installed on the fuel injection pump. By disconnecting the "ignition", the voltage supply to the solenoid valve is stopped, and it closes the fuel supply channel. When the engine is started, the immobilizer releases the solenoid valve and the engine starts.
Driving in winter
When the ambient temperature drops, the fluidity of diesel fuel deteriorates due to the condensation of paraffin in it. Diesel fuel becomes thick as honey. For this reason, diesel fuel manufacturers add special additives to it in winter, which improve the fluidity of diesel fuel and guarantee engine start up to temperatures of about -20°C.
In order to prevent thickening, an electric diesel fuel heater (1) is installed before the fuel filter. The heater is switched on automatically by means of a built-in thermal switch at a temperature below 0°C. At the same time, the thermal switch protects against possible fuel overheating in the event of a malfunction. This ensures reliable operation at all temperatures.
Measures to improve the composition of exhaust gases
To reduce the condensation of nitrogen oxides (NOx) in the exhaust gases, the diesel fuel injection system is equipped with an exhaust gas recirculation system. The exhaust gas recirculation valve is located in the intake manifold. Its task is to return part of the exhaust gases to the combustion chambers of the engine, thereby reducing the combustion temperature and therefore reducing the concentration of toxic substances in the exhaust gases.
In order to reduce the concentration of harmful substances in the exhaust gases, such as soot particles and hydrocarbons (HC or CH), precise electronic control and the installation of oxidation catalysts are necessary. The electronic control unit receives information from various sensors and regulates the injection process in accordance with specified databases.
One sensor determines the position of the fuel injection pump lever, controlled by the gas pedal.
There is an inductive sensor on the engine flywheel. It provides information about the engine speed.
The control unit of the diesel fuel injection system selects the optimal injection moment in all engine operating modes by moving the electromagnetic cold start switch and the electromagnetic partial load valve in the high-pressure fuel pump.
The exhaust gas recirculation system is controlled by the control unit using two valves, a vacuum converter and an exhaust gas recirculation valve.
When the engine is cold, the control unit switches on the glow plugs and the pre-glow indicator lamp.