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 air-fuel mixture supply to the engine cylinders are separated: the injectors carry out metered fuel injection into the intake pipe, and the amount of air required at each moment of engine operation is supplied by the throttle assembly. This control method makes it possible to ensure the optimal composition of the combustible mixture at each particular moment of engine operation, which allows obtaining maximum power with the lowest possible fuel consumption and low exhaust gas toxicity. Manages the fuel injection system and the ignition system electronic engine control unit (ECU), which continuously monitors, with the help of appropriate sensors, the engine load, the speed of the vehicle, the thermal state of the engine, and the optimal combustion process in the cylinders.
A feature of the Ford Mondeo injection system is the synchronous operation of the injectors in accordance with the valve timing (the engine control unit receives information from the phase sensors). The controller turns on the injectors in series, and not in pairs, as in asynchronous injection systems. Each nozzle is activated through 720°of crankshaft rotation. However, in starting and dynamic modes of engine operation, an asynchronous method of fuel supply is used without synchronization with the rotation of the crankshaft.
The main sensor for the fuel injection system is the oxygen concentration sensor in the exhaust gases (Lambda probe).
In the exhaust manifold of 1.6 liter engines, combined with two exhaust gas converters (collector), two control oxygen concentration sensors are installed (separately for exhaust paths 1 and 4, 2 and 3 cyl.), which, together with the engine control unit and injectors, form a control loop for the composition of the air-fuel mixture supplied to the engine. Based on the signals from the sensors, the engine control unit determines the amount of unburned oxygen in the exhaust gases and, accordingly, evaluates the optimal composition of the air-fuel mixture entering the engine cylinders at any given time. Having fixed the deviation of the composition from the optimal 1:14 (respectively fuel and air), which ensures the most efficient operation of catalytic converters of exhaust gases, the control unit changes the composition of the mixture using injectors. Since the oxygen sensors are included in the feedback circuit of the engine control unit, the air-fuel ratio control loop is closed. In addition to two control sensors, there are also two diagnostic oxygen concentration sensors installed at the outlet of the converters. According to the composition of the gases that have passed through the converters, they determine the efficiency of the engine control system. If the engine control unit, based on information received from diagnostic oxygen concentration sensors, detects an excess of exhaust gas toxicity that cannot be eliminated by calibrating the control system, then it turns on the engine malfunction warning light in the instrument cluster and stores the error code in memory for subsequent diagnostics.
In the collector of engines 2.0 and 2.3 l (with one neutralizer) one control and diagnostic oxygen concentration sensor was installed.
The fuel tank, molded from a special impact-resistant plastic, is installed under the floor of the body in its rear part and is attached with clamps. In order to prevent fuel vapor from entering the atmosphere, the tank is connected by a pipeline to the adsorber of the fuel vapor recovery system. An electric fuel pump is installed in the flanged hole in the upper part of the tank; branch pipes are made on the right side for connecting a filling pipe and a ventilation hose. From the pump, which includes coarse and fine fuel filters, fuel is supplied to the fuel rail mounted on the engine intake pipe. From the fuel rail, fuel is injected by injectors into the intake pipe.
Fuel lines combined power systems in the form of interconnected steel pipelines and rubber hoses.
Fuel pump submersible, electrically driven, rotary type, with coarse and fine fuel filters, with fuel pressure regulator. The pump is installed in the fuel tank, which reduces the possibility of vapor lock, since the fuel is supplied under pressure, and not under vacuum. The fuel pump supplies fuel from the fuel tank through the fuel line to the fuel rail at a pressure of about 380 kPa (approx. 360 kPa at idle).
Fuel filter full-flow fine filter, installed in the fuel pump module housing. If the filter is clogged, it can be replaced separately, as it is made easily removable.
Pic. 5.62. Fuel rail with injectors and a fuel pressure pulsation compensator for a Duratec Ti-VCT engine with a volume of 1.6 l: 1 – fuel pressure pulsation compensator fastening bolts; 2 – fuel pressure pulsation compensator; 3 - sealing rings of the fuel pressure pulsation compensator; 4 – top sealing rings of injectors; 5 - fuel rail; 6 - nozzle clamps; 7 - lower sealing rings of injectors; 8 - nozzles.
Pic. 5.63. Fuel rail with nozzles and fuel pressure regulator for Duratec Ti-VCT engines with a volume of 1.6 l: 1 - nozzle; 2 - ramp; 3 - nozzle retainer; 4 - nozzle sealing ring; 5 - fuel pressure regulator.
Pic. 5.64. Fuel rail with injectors and fuel pressure regulator for Duratec-HE engines with a volume of 2.0 and 2.3 l: 1 - rail; 2 - nozzle; 3 - nozzle retainer; 4 - nozzle sealing ring.
Fuel rail (pic. 5.62–5.64), which is a hollow tubular part with holes for installing injectors, serves to supply fuel to the injectors and is fixed to the intake manifold. A compensator is also installed on the fuel rail of the 1.6L Duratec Ti-VCT engine 2 (see fig. 5.62) fuel pressure pulsations, and on Duratec-HE engines with a volume of 1.6 liters - regulator 5 (see fig. 5.63) fuel pressure. The nozzles, pressure pulsation compensator and pressure regulator are sealed in their sockets with rubber rings.
The injector rail assembly is inserted with the injector shanks into the intake manifold holes and secured with two nuts.
NOTE: Depending on the version, the fuel pressure pulsation compensator may not have the small O-ring 3 (see fig. 5.62).
Nozzles with their nozzles enter the openings of the intake pipe. The nozzles are sealed in the inlet pipe openings with rubber sealing rings. The nozzle is designed for metered injection of fuel into the engine cylinder and is a high-precision electromechanical valve in which the shut-off valve needle is pressed against the seat by a spring. When an electrical impulse is applied from the control unit to the electromagnet winding, the needle rises and opens the atomizer hole - fuel is supplied to the engine intake pipe. The amount of fuel injected by the injector depends on the duration of the electrical impulse.
Fuel Pressure Pulsation Compensator mounted on Duratec Ti-VCT engine (with variable valve timing) with a volume of 1.6 liters at the end of the fuel rail and serves to maintain a constant fuel pressure in the rail when it drops sharply in the fuel line, caused, for example, by a significant increase in fuel consumption during intensive acceleration of the car.
Fuel pressure regulator, mounted on the fuel rail on Duratec-HE 1.6 L engines, and on the fuel pump on other engines, maintains constant fuel pressure in the center channel of the rail at all engine operating modes. The regulation of the pressure of the fuel supplied to the injectors by a regulator installed on the fuel rail is based on the principle of monitoring the pressure difference between the rail and the intake manifold, which under any conditions should be at least 300 kPa (3 kgf/cm2). The electric fuel pump supply is greater than necessary to keep the system working. Therefore, when the engine is running with the help of a pressure regulator, part of the fuel is constantly drained through the return pipe into the fuel tank. Depending on the vacuum in the intake manifold, the pressure regulator reduces or increases the discharge of excess fuel, maintaining a constant pressure in the rail.
The pressure regulator is a closed cavity divided by a diaphragm into vacuum and fuel chambers.
The vacuum chamber communicates through a vacuum hose with the engine intake manifold, the fuel chamber communicates through a channel in the regulator housing with the fuel rail cavity. During engine operation, under the action of a spring, the regulator valve is closed if the pressure drop in the intake manifold and fuel rail is not more than 0.3 MPa. There is no backflow of fuel - the pressure in the fuel line begins to rise. With pressure drop over 300 kPa (3.0 kgf/cm2) the diaphragm of the regulator 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 pipeline - the pressure decreases. When the engine load increases, operating at a wide throttle opening, fuel consumption increases and the pressure in the fuel rail drops. At the same time, the vacuum in the intake pipe is reduced. The spring presses the pressure regulator valve to the seat, the fuel drain into the fuel tank stops - the pressure rises. These processes are repeated continuously, as a result of which a constant pressure is maintained in the fuel rail.
The pressure regulator installed in the fuel pump module is a precisely calibrated bypass valve, the locking element of which opens when a predetermined pressure in the pressure pipe inside the module is reached, as a result of which excess fuel is drained into the tank directly from the fuel pump module, and the backflow line from the fuel rail missing in the design.
The air filter is installed on the left side of the engine compartment on a special bracket. The filter element is paper, flat, with a large area of the filtering surface. The filter is connected by a rubber corrugated air supply sleeve to the throttle assembly.
Throttle assembly, which is the simplest regulating device, serves to change the amount of main air supplied to the engine intake system, is installed on the inlet flange of the intake pipe and attached with screws.
A molded rubber sleeve is put on the inlet pipe of the throttle assembly, fixed with a clamp and connecting the throttle assembly with the air filter.
The throttle assembly includes a throttle position sensor and a throttle control stepper motor. There is no mechanical connection between the throttle assembly and the throttle control pedal. So-called «electronic» the throttle control pedal transmits information about the degree of depression on the pedal to the electronic engine control unit, which, in turn, taking into account the vehicle speed, the gear engaged, the engine load and the crankshaft speed, opens the throttle valve to the desired angle.
The fuel vapor recovery system prevents fuel vapors from escaping into the atmosphere, which adversely affect the environment.
The system uses the method of vapor absorption by a carbon adsorber. It is installed at the rear of the body base and is connected by pipelines to the fuel tank and the purge valve.
In the engine compartment there is an adsorber purge solenoid valve, which, according to the signals from the engine control unit, switches the operating modes of the system.
Fuel vapors from the fuel tank are constantly discharged through the pipeline and accumulate in the adsorber filled with activated carbon (adsorbent). When the engine is running, it regenerates (recovery) adsorbent by purging the adsorber with fresh air entering the system under the action of vacuum transmitted through the pipeline from the inlet pipe to the adsorber cavity when the purge valve is opened.
The control unit regulates the degree of purge of the adsorber, depending on the mode of operation of the engine, by supplying a signal to the valve with a variable pulse frequency.
Fuel vapor from the adsorber through the pipeline enters the engine intake pipe and burns in the cylinders.
Malfunctions of the fuel vapor recovery system entail idle instability, engine shutdown, increased toxicity of exhaust gases and deterioration in driving performance of the vehicle.
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