- fuel supply system, including a fuel tank, electric fuel pump, fuel filter, fuel pressure regulator, pipelines and a fuel rail with injectors;
- air supply, including the air supply pipe, air filter, throttle assembly, idle speed control valve;
- fuel vapor recovery system, including an adsorber and connecting pipelines.
The functional purpose of the supply system is to ensure the supply of the required amount of fuel to the engine in all operating modes. The engines are equipped with an electronic engine management system with distributed fuel injection. In the distributed injection system, the functions of mixture formation and metering of the fuel-air mixture supply to the engine cylinders are separated: air is supplied by the air supply system, consisting of a throttle assembly and an idle speed regulator, and the amount of fuel required at each moment of engine operation is injected by injectors into the intake pipe. This control method makes it possible to ensure the optimal composition of the combustible mixture at each specific moment of engine operation, which allows for maximum power with the lowest possible fuel consumption and low toxicity of exhaust gases. Controls the fuel injection system (as well as the ignition system) an electronic unit that continuously monitors the engine load, vehicle speed, engine thermal state, and the optimality of the combustion process in the engine cylinders using appropriate sensors.
The fuel vapor recovery system prevents fuel vapors from escaping from the fuel system into the atmosphere, which have an adverse effect on the environment.
The system uses a method of vapor absorption by a carbon adsorber. It is installed in the niche of the right front wing and is connected by pipelines to the fuel tank and the inlet pipe. On the adsorber cover there is an electromagnetic valve for purging the adsorber, which switches the operating modes of the system according to signals from the engine control unit.
Fuel vapors from the fuel tank are constantly removed through a pipeline and accumulate in an adsorber filled with activated carbon (adsorbent). Regeneration occurs when the engine is running (recovery) adsorbent by purging the adsorber with fresh air entering the system under the action of the vacuum transmitted through the pipeline from the inlet pipe to the cavity of the adsorber when the valve opens. The magnitude of the valve opening, and therefore the intensity of the adsorber purge, depend on the angle of rotation of the throttle valve and are determined by the vacuum that occurs in the cavity of the inlet pipe of the running engine.
Fuel vapors from the adsorber enter the engine intake pipe through a pipeline and burn in the cylinders.
Malfunctions of the fuel vapor recovery system lead to unstable idle speed, engine stalling, increased toxicity of exhaust gases and deterioration of the vehicle's driving performance.
5.6. Diagram of the fuel-air mixture control circuit: 1 – exhaust gas oxygen concentration sensor (lambda probe); 2 – exhaust manifold; 3 – engine; 4 – nozzle; 5 – Engine control unit; 6 – catalytic converter of exhaust gases
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The main sensor for ensuring an optimal combustion process is the exhaust gas oxygen concentration sensor (lambda probe). It is installed in the exhaust manifold of the engine and, together with the electronic unit and injectors, forms a circuit for adjusting the composition of the fuel-air mixture supplied to the engine (figure 5.6). Based on the sensor signals, the engine control unit determines the amount of unburned oxygen in the exhaust gases and, accordingly, evaluates the optimality of the fuel-air mixture entering the engine cylinders at each moment in time. Having recorded a deviation of the composition from the optimal 1:14 (fuel and air respectively), ensuring the most efficient operation of the catalytic converter of exhaust gases, the control unit changes the composition of the mixture using injectors. As a result, the control circuit of the fuel-air mixture composition is closed.
Some vehicles have two oxygen concentration sensors: one in the exhaust manifold and the other behind the catalytic converter. The first sensor is the control sensor (based on its signal, the ECU adjusts the fuel supply), and the second one is diagnostic (based on its signal, the ECU evaluates the efficiency of the catalytic converter).
The fuel tank is molded from petrol-resistant plastic, installed under the body floor in its rear part and is secured with two bolts and two nuts. In order to prevent fuel vapors from entering the atmosphere, the tank is connected to the adsorber by a pipeline. An electric fuel pump is installed in the flange opening in the upper part of the tank. From the pump, fuel is supplied through the pressure regulator to the fuel filter installed on the end of the fuel tank, and from there it enters the engine fuel rail, secured to the intake pipe. From the fuel rail, fuel is injected by nozzles into the intake pipe.
Fuel lines of the fuel system are tubes that connect various elements of the system.
Attention! It is prohibited to replace steel pipelines with hoses, copper or aluminum tubes, since only steel pipelines meet the operating conditions at high pressure and vibration. The hoses of the fuel system are made using a special technology from oil- and petrol-resistant materials. The use of hoses that differ in design from those recommended may lead to failure of the fuel system, and in some cases, to a fire. Round sealing rings are used in the connections of pipelines with elements of the fuel system. The use of seals of a different design is prohibited.
The fuel pump module includes an electric pump...
...a fuel pressure regulator that maintains a constant fuel pressure in the central channel of the fuel
ramps in all engine operating modes and does not allow the pressure in the fuel rail to be exceeded...
...and the fuel level indicator sensor.
The fuel pump module delivers fuel and is located in the fuel tank, reducing the possibility of vapor lock as the fuel is delivered under pressure rather than vacuum.
Fuel pump of submersible type, with electric drive, rotary type. The pump of non-separable design is not subject to repair, in case of failure it must be replaced.
Fuel filter 1 (figure 5.7) fine cleaning - full-flow, secured with clamp 7 on the fuel tank in its front part. The filter is non-separable, consists of a steel housing with a paper filter element.
5.7. Location of the fuel filter on the vehicle: 1 – fuel filter; 2 – Pipeline tips; 3 – fuel supply line; 4 – fuel drain pipe; 5 – fuel outlet line; 6 – fuel tank; 7 – fuel filter mounting clamp
Ramp 2 injectors (figure 5.8) is a cast hollow part with holes for installing injectors 3 and with a supply nipple 5 for connecting the high-pressure fuel line. The injectors are sealed in their sockets with rubber rings 4 and secured with spring clamps 1. The ramp with injectors in assembly is inserted with the tails of the injectors into the holes of the intake pipe and secured with two bolts.
5.8. Injector ramp: 1 – nozzle retainer; 2 – ramp; 3 – nozzle; 4 – injector sealing ring; 5 – nipple for connecting the high-pressure fuel line
Nozzles (figure 5.9) are attached to the ramp from which fuel is supplied to them, and their sprayers enter the holes of the inlet pipe. In the holes of the ramp and the inlet pipe, the injectors are sealed with rubber sealing rings 1 and 2. The injector is designed for metered injection of fuel into the engine cylinder and is a high-precision electromechanical valve. Fuel under pressure comes from the ramp through channels inside the injector body to the shut-off valve. The spring presses the needle of the shut-off valve to the conical hole of the sprayer plate, holding the valve in the closed position. The voltage supplied from the engine control unit through plug terminals 3 to the winding of the injector electromagnet creates a magnetic field in it, drawing the core together with the needle of the shut-off valve into the electromagnet. The conical annular hole in the sprayer plate opens, and fuel is injected through the diffuser of the sprayer body into the intake channel of the cylinder head and then into the engine cylinder. After the electrical impulse ceases to flow, the spring returns the core and the needle of the shut-off valve to their original state – the valve is closed. The amount of fuel injected by the injector depends on the duration of the electrical impulse.
5.9. Fuel injection system injector: 1 – upper sealing ring; 2 – lower sealing ring; 3 – plug-in terminals of the electromagnet winding
The fuel pressure regulator installed in the fuel pump module maintains constant fuel pressure in the engine fuel system in all engine operating modes. The electric fuel pump supply is greater than necessary to ensure the system's operability. Therefore, when the engine is running, part of the fuel is constantly drained into the fuel tank by the pressure regulator.
The air filter is installed in the center of the engine compartment.
The air filter element is paper, round, with a large filtering surface area.
The throttle assembly is the simplest control device and serves to change the amount of primary air supplied to the engine intake system. It is installed on the inlet flange of the intake pipe. An air filter is put on the inlet pipe of the throttle assembly, the connections of the throttle assembly with the intake pipe and air filter are sealed with rubber gaskets.
The throttle body has a hole for supplying additional air to the idle speed regulator.
5.10. Throttle assembly: 1 – idle speed controller; 2 – throttle valve drive lever; 3 – throttle valve; 4 – throttle position sensor; 5 – throttle body
In building 5 (figure 5.10) a flap 3 rotating on an axis is installed. At one end of the axis a sensor 4 of the throttle position of the engine management system is installed, at the other - a lever 2, to which an intermediate rod of the throttle drive is connected. On the housing 5 an idle speed regulator 1 is fixed, dosing the air flow with the throttle valve closed.
During operation, the throttle assembly does not require maintenance or adjustment; just monitor the condition of the rubber seals to avoid air leakage.
The idle speed control valve maintains the set engine idle speed with the throttle valve fully closed during starting, warming up and when the load changes when auxiliary equipment is turned on.
The regulator changes the amount of additional air supplied to the intake system in addition to the throttle valve, and is an electromechanical valve attached with two bolts to the flange of the throttle body. The regulator valve seat and channels made in the flange of the throttle assembly form a system for supplying additional air, bypassing the throttle valve.
5.11. Idle speed controller: 1 – valve; 2 – regulator body; 3 – stator winding; 4 – lead screw; 5 – stator winding plug terminal; 6 – ball bearing; 7 – stator winding housing; 8 – rotor; 9 – spring
The engine control unit, having processed the signals from the sensors, determines the need to open valve 1 (figure 5.11) regulator and transmits pulses to plug terminal 5 of winding 3 of the regulator stator. With each control pulse, rotor 8 rotates by a certain angle, moving valve 1 relative to the seat with the help of lead screw 4. Additional air enters the intake pipe through channels in the throttle assembly. By determining the vacuum in the engine intake pipe, the control unit strives to maintain it at a given level, periodically opening and closing the idle speed regulator valve. This makes it possible to ensure the supply of a constant amount of additional air to maintain a constant idle speed. By changing the amount of opening and closing of the regulator valve, the control unit compensates for a significant increase or decrease in the amount of air supplied, caused by its suction through a leaky intake system or, conversely, clogging of the air filter.
The inclusion of additional units causes an increase in engine load, accompanied by a decrease in idle speed and a change in the vacuum in the intake pipe, which is also compensated for by the control unit using the regulator.