The fuel pump provides a continuous supply of fuel through a cartridge filter into the fuel line under slight excess pressure. The fuel pressure regulator provides constant pressure on the injection injectors. Excess fuel is returned to the fuel tank through the return line. Such a continuous supply system allows to reduce the fuel temperature and prevent its evaporation.
The injectors are opened and closed by command from the electronic control unit (ECU), which calculates the moment and duration of injection based on an analysis of incoming information signals about engine speed, position and speed of the throttle valve, depth of vacuum in the intake manifold, intake air temperature, coolant temperature, exhaust gas composition, etc.
The air sucked into the engine passes through the air cleaner, inside which a replaceable filter element made of thick paper is installed. The temperature of the sucked air is regulated by means of a vacuum valve installed in the air cleaner casing and allowing the outside air to be mixed with the air coming through the heater casing located above the exhaust manifold.
The temperature of the air entering the throttle body is measured by a sensor installed on the intake manifold. In parallel, the sensor monitors the absolute pressure in the manifold. All information is sent to the ECU and used by it to determine the optimal air-fuel mixture in accordance with the current operating parameters of the engine.
The engine idle speed is controlled partly by the electronic throttle position module mounted on top of the throttle body, and partly by the ignition system, by changing the ignition timing settings. In view of the above, there is no need for manual speed adjustments and the system design does not provide for this. Information about the position and speed of the throttle valve is supplied to the ECU by a special sensor, sometimes also called a throttle potentiometer. The sensor is located on the left wall of the throttle body.
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The oxygen content in the exhaust gases is continuously monitored by the ECU via a λ-probe installed in the front section of the exhaust system (ahead of the catalytic converter). By analyzing the incoming information, the ECU issues commands to adjust the ignition timing and injection duration, thereby forming an optimal air-fuel mixture. As a result, there is no longer any need for manual adjustment of the CO content in the exhaust gases. The standard equipment of all models considered in this Manual includes a catalytic converter.
In addition to the functions listed above, the ECU controls the operation of the fuel evaporative emission system.
It should be noted that diagnostics of failures of all engine management systems is possible only with the help of a special electronic reader. In case of any malfunctions of the system, you should immediately contact the specialists of the Skoda branded service center, who will read and decipher the codes of faults detected by the self-diagnosis system recorded in the ECU memory unit. The procedure for replacing failed system components is described in the following Sections of the Chapter.