Vortex chamber
1 – nozzle; 2 – glow plug; 3 – vortex chamber; 4 – channel; 5 – piston
When a diesel engine is running, fresh air, having passed through a filter, is sucked into the cylinders and is strongly compressed, as a result of which it is heated to a high temperature. When the piston approaches the top dead center position in the compression stroke, diesel fuel is injected into the compressed and heated air and its self-ignition occurs.
To facilitate starting a cold engine, two autonomous systems are used. One of the systems maintains increased idle speed during a cold start until the engine warms up.
The second system serves to improve fuel ignition in the cylinders at the moment of starting. Glow plugs are installed in the swirl chambers of each cylinder. Before starting the engine, voltage is supplied to them, which is indicated by the lighting of the control lamp on the instrument cluster. Within a few seconds, the plugs heat up to a high temperature and the control lamp goes out, which serves as a signal to start the engine. The hot plugs raise the temperature in the swirl chamber and facilitate the ignition of the fuel. It should be noted that the plugs do not turn off immediately after starting the engine, but after some time, allowing the engine to reach normal operating mode. The failure of even one plug leads to difficult starting of the engine with interruptions in operation and strong vibration.
The fuel system is designed to clean and supply atomized fuel to the engine cylinders in the amount required for the corresponding operating mode.
The fuel system includes a rear-mounted fuel tank, fuel filter, high-pressure fuel pump, injectors, high-pressure and low-pressure fuel lines.
The fuel pump takes fuel from the tank and sends it to the filter. The filter retains mechanical impurities and water contained in the fuel. A manual fuel pump is mounted in the fuel pump body. After being cleaned in the filter, the fuel goes to the high-pressure fuel pump.
The amount of fuel supplied to the cylinders is regulated by a metering device controlled by a cable from the accelerator pedal. The injection advance angle changes depending on the engine speed by a mechanical centrifugal regulator built into the high-pressure fuel pump.
The high-pressure fuel pump does not require maintenance. The fuel pump is driven from the crankshaft on an engine with a working volume of 1.6 dm³ via three spur gears or on an engine with a working volume of 1.8 dm³ – via an additional toothed belt.
There is an electromagnetic valve to stop the engine. When the engine starts, 12 V is supplied to the valve winding, the valve opens and passes fuel to the pump and injectors. When the engine is turned off by turning the key in the ignition switch, the fuel valve is turned off and the fuel supply is cut off.
The fuel pump delivers fuel under high pressure through pipelines to the injectors, which are installed in the cylinder head near the combustion chambers. The injectors inject fuel into the swirl chambers, where the fuel is ignited.
The injectors are a valve that opens at a strictly defined fuel pressure (110–120 bar). The atomizer, located at the lower end of the injector, forms a spray of the required fuel shape. The fuel is cut off by a needle under the action of the injector spring. The atomizer and needle are precision units and require careful handling during repair. Excess fuel after the cutoff leaks along the needle, lubricating it, and is discharged into the tank through the return line.
The serviceability and correct adjustment of the injectors are very important for the normal operation of the engine. If the injector spray does not provide the required torch shape or there is a bad cut-off, the engine begins to vibrate, strong mechanical knocks appear, and smoking increases.
Attention! Injection pressure is an adjustable parameter. During engine operation, injection pressure often drops, so the injector must be checked periodically and, if necessary, adjusted.
It should be noted that the nozzles from different engine models are externally identical, but have different characteristics, in particular, the shape of the torch, so you should use only those new nozzles that are designed for a given model.
Since November 1987, the 1.6 dm³ engine has been equipped with an exhaust gas recirculation system. Part of the exhaust gases enters the engine cylinders and is burned. The valve system ensures the correct dosing of the recirculated gases. The temperature sensor, located on the thermostat housing of the cooling system, interrupts the system at an engine temperature below 60°C. The exhaust gas recirculation system does not require maintenance. Only after removing the high-pressure fuel pump can the vacuum control valve be checked and, if necessary, adjusted.