Features of the fuel system design
The fuel system includes elements of the following systems:
Fuel supply system - fuel supply system, including fuel tank 4 (Fig. 1), electric fuel pump 2, pipelines 5, 6 and 13, hoses 12, fuel rail 8 with injectors 7 and fuel pressure regulator 9, as well as fuel filter 11;
– air supply system, including air filter 1 (Fig. 2), air supply pipe 2, throttle assembly 3; – fuel vapor recovery system, including adsorber 4 and connecting pipelines.
The fundamental feature of the VAZ-2123 engine fuel system is the absence of a carburetor in it, which combines the functions of mixture formation and metering the supply of fuel-air mixture to the engine cylinders.
In the distributed injection system installed on this engine, these functions are separated
– injectors perform metered fuel injection into the intake pipe, and the supply The air required at each moment of engine operation is provided by a system consisting of a throttle assembly and an idle speed regulator.
The fuel injection system and ignition system are controlled by an electronic engine control unit, which continuously monitors the engine load, vehicle speed, engine thermal state, and the optimal combustion process in the engine cylinders using appropriate sensors.
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.
The fuel system is an integral part of the engine management system.
Fuel tank 4 - (see Fig. 1) welded, stamped, secured in the luggage compartment with bolts and nuts.
An electric fuel pump is installed in the upper part of the fuel tank, combined with a fuel level sensor.
From the pump, fuel is supplied to the fuel filter installed in the engine compartment, and from there it enters the engine fuel rail, secured to the engine intake pipe.
From the fuel rail, fuel is injected by injectors into the intake pipe.
Excess fuel is drained into the fuel tank through the fuel pressure regulator installed at the rear end of the fuel rail.
Fuel pump 2 - with an electric drive, two-stage, rotary type, installed in the fuel tank, which reduces the possibility of vapor locks, since the fuel is supplied under pressure, and not under the action of vacuum.
It provides fuel supply under pressure more than 284 kPa.
Fuel filter 11 is built into the supply line between the electric fuel pump and the fuel rail and is installed in the engine compartment on the front panel of the body on a car manufactured before 2009.
After 2009. The filter is installed under the bottom of the car, near the rear right wheel.
The filter is non-separable, has a steel body with a paper filter element.
The 8 injector ramp is a hollow bar with injectors and a fuel pressure regulator installed on it.
The injector ramp is fixed to the inlet pipe.
At the rear end of the ramp there is a valve for controlling the fuel pressure, closed with a threaded plug.
Injectors 7 - 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 sealeded with rubber sealing rings.
The injector is an 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 nozzle hole through which 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 regulator 9 - is installed on the fuel rail and is designed to maintain a constant pressure difference between the air pressure in the intake pipe and the fuel pressure in the rail.
The regulator consists of valve 5 (Fig. 4) with diaphragm 4, pressed by a spring to the seat in the regulator body.
When the engine is running, the regulator maintains the pressure in the injector rail within 284–325 kPa.
The regulator diaphragm is exposed to fuel pressure on one side, and to pressure (vacuum) in the intake pipe on the other.
When the pressure in the intake pipe decreases (the throttle valve closes), the regulator valve opens at a lower fuel pressure, bypassing excess fuel through the drain line back to the tank.
The fuel pressure in the rail decreases.
When the pressure in the intake pipe increases (when the throttle valve opens), the regulator valve opens at a higher fuel pressure and the fuel pressure in ramp increases.
Air filter 1 - (see Fig. 2) is installed in the front part of the engine compartment on rubber supports.
The filter element is paper, flat, with a large filtering surface area.
The filter is connected to the throttle assembly by a corrugated air supply pipe, consisting of two parts.
A mass air flow sensor is installed between the pipe and the filter.
The throttle assembly 3 - (Fig. 1) is fixed to the receiver.
It doses the amount of air entering the intake pipe.
The air flow into the engine is controlled by the throttle valve, connected to the accelerator pedal drive.
The throttle pipe includes a throttle position sensor 4 (Fig. 5) and an idle speed regulator 5.
In the flow part of the throttle pipe (in front of the throttle valve and behind it) there are vacuum extraction holes necessary for the operation of the crankcase ventilation system and the adsorber of the gasoline vapor recovery system.
The idle speed regulator 5 - (see Fig. 5) regulates crankshaft speed at idle, controlling the amount of air supplied bypassing the closed throttle valve.
It consists of a two-pole stepper motor and a cone valve connected to it.
The valve extends or retracts according to the controller signals.
When the regulator needle is fully extended (which corresponds to 0 steps), the valve completely blocks the air passage.
When the needle is retracted, the air flow is proportional to the number of steps the needle moves away from the seat.
The fuel vapor recovery system uses a method of vapor absorption by a carbon adsorber 4 (see Fig. 1).
It is installed in the engine compartment and connected by pipelines to the fuel tank and throttle pipe.
On the cover of the adsorber 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.
When the engine is not running, the electromagnetic valve is closed and gasoline vapors from the fuel tank go through the pipeline to the adsorber, where they are absorbed by granular activated carbon.
When the engine is running, the adsorber is purged with air and the vapors are sucked to the throttle assembly, and then into the intake pipe for combustion during the working process.
The controller controls the purge adsorber, including the electromagnetic valve located on the adsorber cover.
When voltage is applied to the valve, it opens, releasing vapor into the intake pipe.
The valve is controlled using pulse-width modulation.
The valve turns on and off at a frequency of 16 times per second (16 Hz).
The higher the air flow, the longer the duration of the valve activation pulses.
The controller turns on the adsorber purge valve when all of the following conditions are met:
- – the coolant temperature is above 75 °C;
- – the vehicle speed exceeds 10 km/h.
After the valve is turned on, the speed criterion changes. The valve will only switch off when the speed drops to 7 km/h;
– the throttle opening exceeds 4%. This factor is of no further importance if it does not exceed 99%.
When the throttle valve is fully open, the controller turns off the purge valve of the adsorber.
Failures in the fuel vapor recovery system lead to instability of idle speed, engine stalling, increased toxicity of exhaust gases and deterioration of driving qualities of the car.
The following system failures are possible:
- – failure of the electromagnetic purge valve;
- – damage to the adsorber;
- – overflow of the adsorber, collecting more than 60 g of fuel (the weight of a new adsorber is no more than 1.1 kg);
- – damage or improper connection of hoses.