The fuel system includes elements of the following subsystems:
- fuel supply, including the fuel tank, the electric fuel pump with filter, the fuel pressure regulator, the pipes and the fuel rail with injectors;
- air supply system, consisting of the air supply hose, the air filter, the throttle body, the idle speed regulator;
- fuel vapour recovery system, including the canister, the control valve and the connecting pipes.
The function of the supply subsystem 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 supply of the air-fuel mixture to the engine cylinders are separated.
Air is supplied by the air supply subsystem, consisting of the throttle body, and the amount of fuel required at each moment of engine operation is injected by the injectors into the intake pipe.
This method of control makes it possible to ensure the optimum composition of the combustible mixture at each specific moment of engine operation, which allows maximum power to be obtained with the minimum possible fuel consumption and low exhaust gas toxicity.
The fuel injection system (as well as the ignition system) is controlled by an electronic unit that continuously monitors, using appropriate sensors, the engine load, the vehicle speed, the thermal state of the engine and the optimality of the combustion process in the engine cylinders.
The fuel pump module includes an electric pump, a fine fuel filter, a fuel pressure regulator and a fuel level sensor.
The fuel pump module ensures the fuel supply and is installed in the fuel tank, which reduces the possibility of vapour lock formation, since the fuel is supplied under pressure and not under the action of vacuum.
The fuel pump is of the submersible type, with an electric drive, of the rotary type.
The pump is of non-detachable construction, is not repairable; if it fails, it must be replaced.
The fuel level sensor is attached to the body of the fuel module.
The fuel level sensor is a variable resistor whose resistance depends on the movement of the float.
The sensor controls the operation of the fuel level indicator and the minimum fuel level warning lamp located in the instrument cluster.
The fuel pump is located inside the body of the fuel module.
The pump is electric, of the vortex type.
It is switched on by command of the electronic engine control unit when the ignition is switched on and supplies fuel to the line under a pressure (about 6.0 bar) exceeding the working pressure in the fuel rail.
The fuel, passing through the pump, lubricates and cools the pump during its operation.
Therefore it is prohibited to switch on the pump even briefly if there is no fuel in the tank.
From the pump, the fuel is supplied through a corrugated plastic pipe to the filter and the fuel pressure regulator, which are part of the fuel module.
The fuel filter (non-replaceable) is intended for cleaning the fuel from mechanical impurities.
If the filter becomes clogged, the fuel module must be replaced.
The fuel pressure regulator is a valve which opens when the specified fuel pressure in the line is exceeded and releases part of the fuel into the tank.
The fuel pressure in the line with the ignition on and the engine not running must be about 3.2 bar.
If the pressure regulator fails, the fuel module must be replaced.
From the filter body, the fuel is supplied through a corrugated plastic pipe to the module cover.
The end of the fuel pipe running under the vehicle floor is connected to the outlet union of the fuel module cover.
The other end of the fuel pipe in the engine compartment is connected to the union of the fuel rail (vehicle with 1.6 engine) or to the union of the fuel filter (vehicle with 2.0 engine).
The fuel filter is secured in the engine compartment on the right-hand side.
The other union of the fuel filter is connected by a pipe to the union of the fuel rail.
In accordance with the vehicle maintenance schedule, the fuel filter located in the engine compartment must be replaced every 120,000 km of mileage.
The fuel rail is a pipe made of high-strength heat-resistant plastic, on which the injectors are installed.
The rail is attached to the intake pipe with two bolts.
The fuel rails and injectors of the 1.6 and 2.0 engines differ from each other.
The fuel under pressure is supplied to the cavity of the rail, and from there through the injectors — into the channels of the intake pipe.
The injector is a solenoid valve that injects fuel into the channel of the intake pipe when voltage is applied to it and closes under the action of the return spring when de-energized.
At the outlet of the injector, a sprayer with four holes is provided, through which the fuel is injected into the channels of the intake pipe.
The operation of the injectors is controlled by the ECU.
The injectors are sealed in the rail and intake pipe by rubber rings and secured on the rail by metal clips.
In the event of a break or short circuit of the winding, the injector must be replaced.
The air is supplied to the channels of the engine cylinder head through the air intake, the resonator, the air filter, the throttle body, the receiver and the intake pipe.
The resonator ensures the absorption of air pressure waves and the reduction of intake noise.
The air filter housing is made of high-strength heat-resistant plastic and is secured on the rear side of the engine.
A replaceable filter element (paper) is adjacent to the air supply hole in the housing and is closed by a cover.
A neck is provided in the filter housing, which is connected to the stub of the throttle body.
The throttle body is the simplest regulating 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 manifold.
The stub of the body of the air intake chamber is fitted onto the inlet stub of the throttle body.
The throttle body includes a stepper electric motor for controlling the throttle valve.
There is no mechanical connection between the throttle body and the throttle control pedal.
The so-called «electronic» throttle control pedal transmits information about the degree of pedal depression to the electronic engine control unit, which, in turn, taking into account the vehicle speed, the engaged gear, the engine load and the crankshaft speed, opens the throttle valve by the required angle.
On the K4M engine, the valve is driven by a cable.
At one end of the throttle shaft, lever 3 is installed, to which the intermediate drive rod is connected, at the other — the valve position sensor 6.
On the F4R engine, the throttle valve is driven by a stepper electric motor.
There is no mechanical connection between the throttle body and the throttle control pedal.
The so-called «electronic» throttle control pedal transmits information about the degree of pedal depression to the electronic engine control unit, which, in turn, taking into account the vehicle speed, the engaged gear, the engine load and the crankshaft speed, opens the valve by the required angle.
The idle speed regulator of the K4M engine maintains the specified idle speed of the engine with the throttle valve fully closed during its start-up, warming up and when the load changes during the switching on of auxiliary equipment.
The regulator changes the amount of additional air supplied to the intake system in addition to the throttle valve, and is an electromechanical valve secured by two screws to the flange of the air filter housing.
The regulator valve seat and channels provided in the filter flange form the additional air supply system, bypassing the throttle valve.
The engine control unit, after processing the signals from the sensors, determines the need to open the regulator valve (figure) and transmits pulses to the stator winding of the regulator.
At each control pulse, the rotor turns through a certain angle, moving the valve relative to the seat by means of a lead screw.
Additional air enters the intake pipe.
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, by clogging of the air filter.
Switching on additional units causes an increase in the load on the engine, accompanied by a decrease in idle speed and a change in the vacuum in the intake pipe, which is also compensated by the control unit using the regulator.
The throttle body of the F4R engine has no idle speed regulator.
The required crankshaft speed in idle mode is maintained by the electronic control unit by changing the throttle valve opening angle using a stepper electric motor.
After passing through the throttle body, the air enters the receiver, made of high-strength heat-resistant plastic.
The receiver is secured on top of the cylinder head cover.
From the common cavity of the receiver, the air passes through four channels to the channels of the intake pipe.
The fuel vapour recovery system used in the fuel system includes the canister, the canister purge solenoid valve and the connecting pipes.
From the fuel tank, petrol vapours pass through a plastic pipe running under the vehicle floor into the canister (installed behind the front bumper, in front of the right wheel arch), where they are absorbed by the sorbent (activated carbon).
The canister purge solenoid valve is installed on top of the canister.
The valve is connected by a plastic pipe to the space downstream of the throttle valve of the throttle body.
When the engine is stopped, the purge solenoid valve is closed, and in this case the canister does not communicate with the throttle body.
The ECU, by controlling the solenoid valve, carries out purging of the canister after the engine has run for a specified period from the moment of switching to the closed-loop fuel supply control mode (the control oxygen sensor must be warmed up to the required temperature).
The valve connects the cavity of the canister with the throttle body, and purging of the sorbent occurs: the petrol vapours mix with air and pass through the throttle body and the receiver into the intake pipe and then into the engine cylinders.
The greater the air consumption by the engine, the longer the duration of the ECU control pulses and the more intensive the purging.
