The electronic engine management system consists of a fuel tank, an electric fuel pump, a fuel filter, fuel supply and return hoses, a throttle body, a fuel line, a fuel pressure regulator, four electronically controlled fuel injectors and an electronic control device (ECU) along with sensors, actuators and electrical wires.
The fuel tank on Sedan and Coupe models is mounted vertically behind the back of the rear seat. On Wagon models, the fuel tank is mounted horizontally under the trunk floor. The fuel level sensor is attached to the top of the fuel tank and can be replaced without removing the fuel tank.
An electric fuel pump with a circulation chamber is installed under the floor at the rear of the vehicle. The fuel pump motor is constantly cooled by the fuel passing through it. The fuel pump has a one-way valve that, by shutting off the fuel system, maintains pressure in it even after the fuel pump is turned off. The valve also isolates the fuel tank from the rest of the fuel system. The pump also contains a pressure relief valve that limits the pressure in the fuel system.
The fuel pump delivers fuel through the fuel filter to the fuel line at a pressure greater than the pressure in the fuel system. The pressure regulator maintains a constant desired pressure in the fuel system and returns excess fuel to the fuel tank through the fuel return line. This constant circulation of the fuel reduces the temperature of the fuel and prevents the vaporization of the fuel.
The fuel injectors are solenoid valves opened and closed by an electronic control device (ECU), which determines the opening time and duration of fuel injection depending on the engine speed, throttle position, the amount of incoming air mass, the temperature of the air entering the engine, the temperature of the coolant and oxygen in the exhaust gases based on information received from sensors installed on engine and around it.
Air enters the engine through an air filter with a replaceable filter element. The temperature of the air entering the engine is regulated by a vacuum valve installed in the air filter. The vacuum valve mixes cold air entering the engine with air heated by the exhaust manifold. This valve, unlike a vane-type air flow meter, is sensitive to air density. This means that when the vehicle is operated at high altitudes, the vacuum is automatically taken into account without the need for a separate barometric air pressure measurement.
The idle speed is controlled by the idle speed control unit, which is mounted on the side of the throttle body, and the ignition system, which regulates the idle speed by changing the ignition timing.
The oxygen content in the exhaust gases is constantly monitored by the ECU based on the signals of the Lambda sensor, which is installed on the exhaust pipe. Based on information from the Lambda sensor, the ECU determines the moment and duration of fuel injection in order to maintain the optimum fuel mixture ratio. There is also no need to manually adjust the CO content in the exhaust gases. In addition, to reduce the emission of harmful substances into the atmosphere, some models are equipped with a catalytic converter.
On some models, the ECU also controls the operation of the activated carbon filter.
Troubleshooting on the HFM electronic engine management system is possible only with the use of special diagnostic equipment.
Precautions
The fuel system is under constant pressure, even after the engine has been switched off, so any work on the fuel system must be relieved of pressure.
To prevent the possibility of accidental short circuits in the electrical circuit and damage to the electronic components of the fuel injection system, always remove the ground wire from the battery.
Warning! Gasoline is extremely flammable and explosive, so care must be taken when working on any part of the fuel system.
Warning! The container in which the fuel was located contains fuel vapors and is potentially explosive.
Attention! Work on the fuel system must be carried out in a well-ventilated area, for which all windows and doors can be opened to create a draft.
Attention! When working on the fuel system, do not use open flames, electric welding, or tools that may generate sparks. Make sure there is a charged fire extinguisher in the immediate vicinity of the workplace.
Attention! Use goggles to protect your eyes from getting fuel in them. If fuel comes into contact with skin, wash the area with plenty of water.
Attention! Keep the fuel system clean as dirt entering the fuel system passages can block them and prevent the engine from running properly.