4. When operating the vehicle in low ambient temperatures, the temperature of the air inside the cylinders after compression may not be sufficient for self-ignition of the fuel. In this case, it is necessary to preheat the incoming air flow. To do this, glow plugs are installed in the combustion chambers, heating them to the required temperature. The duration of pre-glow depends on the outside temperature and is controlled by the engine management system via a pre-glow relay. When the glow plugs are activated, the corresponding control lamp lights up on the instrument panel (see chapter «Controls and methods of operation»).
5. For diesel engines, there are three fuel injection methods: swirl chamber injection, pre-chamber injection and direct injection.
6. With vortex chamber and pre-chamber methods, fuel is injected into the preliminary chamber (fort chamber) of the corresponding cylinder where it mixes with air and creates a ready-made working mixture, while part of the fuel immediately ignites and burns out. Due to the turbulence of the air flow and heating during the combustion of part of the fuel, the working mixture becomes more homogeneous and heated. This ensures the completeness of combustion of fuel when it enters the cylinder and more «soft» engine operation. The main disadvantage of these injection methods is the complexity of the engine design. Direct injection continues to be the most common and most economical.
7. With direct injection, fuel enters directly into the combustion chamber through the injector nozzle. Each atomizer has, as a rule, 4-6 very thin holes, drilled at different angles, through which the fuel is sprayed in specially given directions. Usually there is a swirl chamber in the bottom of the piston. Swirl chambers can have a different shape, which is consistent with the directions of fuel spraying, contributes to better mixture formation and more efficient combustion of the working mixture. This method is used on all diesel engines considered in this Manual.
8. On Y17DT engines (L) fuel is sucked from the fuel tank by the high pressure fuel distribution pump (injection pump). The injection pump creates the high pressure required for injection (about 900 bar) pressure and supplies fuel through the nozzles to the engine cylinders in the order of the cylinders. First, a small amount of fuel is pre-injected, which, when burned, prepares the conditions for the injection of the main portion of the fuel. This results in more «soft» and uniform combustion of fuel, as on engines with swirl chamber injection.
9. Z13DT / Z17DTH engines use a direct injection system «Common Rail» - common for all cylinders fuel distribution line (see resist. illustration). Fuel is drawn from the fuel tank by the electric fuel pump and delivered to the high pressure fuel pump (injection pump). This system relieves the injection pump from the function of distributing fuel, which allows the pump to create a very high (approx. 1400 bar) pressure, - this contributes to a finer atomization of the fuel, thereby improving the process of mixture formation in the cylinders and increasing the efficiency of combustion of the working mixture. fuel distribution line (Common Rail) made in the form of a manifold, from which fuel is supplied to individual nozzles.
15.9. Common rail injection system (on the example of Z13DT engines): 1. Fuel filter; 2. Pressure regulator; 3. High pressure fuel pump; 4. Fuel distribution line (Common-Rail); 5. Pressure sensor; 6. Nozzle; 7. Fuel tank; 8. Electric fuel pump; 9. Electronic module of the engine management system; Dotted arrows direct electrical signals; Short arrows fuel flow direction
10. On all engines, before fuel enters the injection pump, it is cleaned in the fuel filter from contaminants and water. The engines are equipped with injectors with electromagnetic controls that receive signals from the engine management system, which regulates the amount of fuel supplied to the cylinder.
11. HPFP does not require special maintenance work. All moving parts of the fuel system are lubricated with diesel fuel. The injection pump is driven from the crankshaft through a timing belt or chain.
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