- fuel supply system, including a fuel tank, electric fuel pump, fuel filter, fuel pressure regulator, pipelines and a fuel rail with injectors;
- air supply, which includes an air filter, throttle assembly, idle speed control valve;
- fuel vapor recovery system consisting of an adsorber, an adsorber purge valve and connecting pipelines.
Note: The fuel vapor recovery system is described in a separate subsection (see "Fuel vapor recovery system"), since it serves only to meet environmental requirements for reducing toxicity.
The functional purpose of the fuel supply system is to ensure the supply of the required amount of fuel to the engine in all operating modes. The engine is equipped with an electronic control system with distributed fuel injection. In the distributed fuel injection system, the functions of mixture formation and dosing 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 required amount of fuel 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 obtaining maximum power with the lowest possible fuel consumption and low toxicity of exhaust gases. The fuel injection system (and the ignition system too) is controlled by 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 main sensor for ensuring an optimal combustion process is oxygen concentration sensor in the exhaust gases (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. 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 (respectively, fuel and air), which ensures the most efficient operation of the catalytic converter.
Fuel tank, molded from gasoline-resistant plastic, is installed under the body floor in its rear part and secured with four bolts. To prevent fuel vapors from entering the atmosphere, the tank is connected by a pipeline to the adsorber. An electric fuel pump is installed in the flange opening in the upper part of the tank. From the pump, fuel is fed to the fuel filter installed in the underhood space on the front shield, and from there it enters the engine fuel rail, secured to the intake pipe. From the fuel rail, fuel is injected by injectors into the intake pipe.
Fuel lines power supply systems are tubes that connect various elements of the system together.
Caution! It is prohibited to replace steel pipelines with hoses, copper or aluminum tubes, since only steel pipelines meet the conditions of operation under high pressure and vibration.
Attention! Fuel system hoses are made using a special technology from oil- and petrol-resistant materials. Using hoses that differ in design from those recommended may result in fuel system failure and, in some cases, fire.
Attention! Round sealing rings are used in pipeline connections with power supply system elements. The use of seals of other designs is prohibited.
Fuel pump module includes an electric pump and a 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 submersible, rotary type, with electric drive. The pump is of non-separable design and cannot be repaired; if it fails, it must be replaced.
Fuel filter fine cleaning - full-flow, fixed in a bracket installed under the body floor in its rear part next to the fuel tank. The filter is non-separable, consists of a steel housing with a paper filter element.
Fuel rail (Fig. 5.14) is a cast hollow part with holes for installing injectors 1, with a flange for installing a fuel pressure regulator 5 and with a nipple for connecting a high-pressure fuel line. The injectors are sealed in the ramp holes and in the inlet pipe sockets with rubber rings 4 and secured with spring clamps 3. The fuel pressure regulator is attached to the ramp flange with a fixing bracket, to which the fuel drain pipe is connected. The ramp with injectors and regulator in assembly is inserted with the tails of the injectors into the holes of the inlet pipe and secured with two bolts.
Fig. 5.14. Fuel rail: 1 – nozzle; 2 – ramp; 3 – nozzle retainer; 4 – injector sealing ring; 5 – fuel pressure regulator
Nozzles (Fig. 5.15) 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 3. 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 spray plate, holding the valve in the closed position. The voltage supplied from the engine control unit through plug terminals 2 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 spray plate opens, and fuel is injected through the spray body diffuser into the cylinder head intake channel and further into the engine cylinder. After the electrical impulse ceases, 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.
.Fig. 5.15 Fuel injection system injector: 1 – upper sealing ring; 2 – plug-in terminals of the electromagnet winding; 3 – lower sealing ring
Fuel pressure regulator, installed on the fuel rail, maintains constant fuel pressure in the central channel of the rail in all engine operating modes. Regulation of the fuel pressure supplied to the injectors is based on the principle of monitoring the value of the pressure difference in the rail and the inlet pipe, which under any conditions should be at least 300 kPa (3.0 kgf/cm²). The supply of the electric fuel pump is greater than necessary to ensure the operability of the system. Therefore, when the engine is running, with the help of the pressure regulator, part of the fuel is constantly drained through the return pipe into the fuel tank. Depending on the vacuum in the inlet pipe, the pressure regulator reduces or increases the drain of excess fuel, maintaining a constant pressure in the rail.
The pressure regulator is a closed cavity divided by a diaphragm into a vacuum and fuel chamber.
The vacuum chamber communicates with the engine intake pipe through a vacuum hose, the fuel chamber communicates with the fuel rail cavity through a channel in the regulator body. During engine operation, the regulator valve is closed under the action of the spring if the pressure difference in the intake pipe and the fuel rail is no more than 0.3 MPa. There is no backflow of fuel - the pressure in the fuel line begins to increase. When the pressure difference exceeds 300 kPa (3.0 kgf/cm²), the regulator diaphragm bends and a gap is formed between the valve and its seat, through which excess fuel is drained into another channel of the regulator connected to the drain pipe - the pressure decreases. With an increase in the load of the engine, operating with a large opening of the throttle valve, fuel consumption increases and the pressure in the fuel rail drops. At the same time, the vacuum in the intake pipe decreases. The spring presses the pressure regulator valve to the seat, the fuel drain into the fuel tank stops - the pressure increases. These processes are repeated continuously, as a result of which a constant pressure is maintained in the fuel rail.
The air filter is installed in the engine compartment.
The air filter element is paper, flat, with a large filtering surface area.
Throttle assembly is an electronic control device and serves to change the amount of main air supplied to the engine intake system. It is installed on the inlet flange of the intake pipe. A molded rubber sleeve is put on the inlet pipe of the throttle assembly, secured with a clamp and connecting the throttle assembly to the air filter.
The throttle assembly includes a throttle position sensor, an absolute pressure sensor, and a stepper motor for controlling the throttle valve. There is no mechanical connection between the throttle assembly and the throttle valve control pedal. The so-called "electronic" throttle valve control pedal transmits information about the degree of pressure on the pedal to the electronic engine control unit, which, in turn, takes into account the vehicle speed, the gear engaged, the engine load, and the crankshaft speed, opens the throttle valve.
Vapor recovery system fuel prevents the release of fuel vapors from the fuel system into the atmosphere, which adversely affects the ecology of the environment.
The system uses a method of absorbing fuel vapors using a carbon adsorber. It is installed on the fuel tank and connected to it by a pipeline and a purge valve.
In the engine compartment, on the cylinder head, there is an electromagnetic valve for purging the adsorber, which switches the operating modes of the system according to a signal from the engine control unit.
Fuel vapors from the fuel tank are constantly removed through a pipeline and accumulate in the adsorber filled with activated carbon (adsorbent). When the engine is running, the adsorbent is regenerated (restored) by purging the adsorber with fresh air entering the system under the action of vacuum transmitted through the pipeline from the throttle assembly diffuser to the adsorber cavity when the purge valve is opened. The controller regulates the degree of purge of the adsorber depending on the engine operating mode, sending a signal with a variable pulse frequency to the valve.
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.
This publication was borrowed from the website (FordBook.ru)