The operation of the injection system closely intersects with the operation of the exhaust gas toxicity reduction system, more detailed information on which can be found in the materials of Chapter Engine management.
Air supply system
The system consists of an air cleaner, air hoses, throttle body, idle speed control device and intake manifold. The intake manifold of both 4-cylinder and V6 engines consists of two sections: the lower (the actual manifold) and the upper (the plenum chamber). The procedures for removing and installing both sections are described in Chapter Engine.
The throttle body has a single-chamber cross-flow design. The lower part of the throttle body is heated by the engine coolant to prevent icing in cold weather. The idle speed adjustment screw is located on top of the throttle body. The throttle position sensor (TPS) is connected to the throttle shaft and monitors the degree of its opening.
At engine idle, the air-fuel mixture is controlled by the idle speed control (IAC) system, which consists of the PCM, the electronic coolant temperature sensor (ECT), the IAC valve and a set of information sensors (intake air temperature sensor [IAT], throttle position sensor [TPS], absolute pressure sensor in the manifold [MAP], etc.) - see also Chapter Engine management. The IAC valve is controlled by the PCM based on information about the current engine load (function of the A/C, power steering, coolant temperature, etc.). The valve regulates the flow rate of air entering the intake manifold through the throttle body. When generating commands to operate the IAC valve, the PCM relies on data coming from various information sensors and allowing it to determine the current vehicle speed, coolant temperature, A/C status (on/off), use of power steering, etc. To avoid disruption of idle speed stability when starting the engine, the IAC valve opens during cranking immediately after starting in order to provide additional air mass to the intake manifold.
Electronic control system
The composition and operating principle of the electronic control system and RSM are discussed in detail in Chapter Engine management.
Fuel supply system
The fuel delivery system components include: electric fuel pump, fuel pressure regulator, fuel injectors, fuel pulsation damper, fuel injectors, fuel rail and fuel system main relay.
The electric fuel pump is located inside the gas tank. The pump sucks fuel from the tank through the filter element, then pumps it through an additional fuel filter and delivers it to the injection injectors. A safety valve is also provided to prevent excessive fuel pressure build-up in the event of a blockage in the tract.
The fuel pressure regulator ensures a constant pressure of fuel supply to the injectors. Excess fuel is directed back to the gas tank via the return line.
Injectors are constant-run electromagnetic valves. The main components of the injector are: a control solenoid, a plunger, and a needle valve. All of these parts are placed in a common housing. When electric current passes through the solenoid coil, the needle valve opens slightly, fuel under pressure fills the cavity of the injector housing and is injected through its nozzle into the combustion chamber of the corresponding cylinder. The amount of injected fuel is determined by the duration of the valve opening time, i.e., the duration of voltage supply to the solenoid coil. In order to limit the current passing through the injectors, resistors are included in the wiring of the circuits of the latter.
The injector activation time is controlled by the PCM. The module memory contains basic valve opening time values for various combinations of input parameters (engine speed and amount of air intake). The necessary information is sent to the module in the form of signals from various engine sensors.
The main relay of the injection system is installed on the left or right in front of the windshield under the fairing panel and consists of two working elements, one of which is the PCM and fuel injector relay, and the second is the fuel pump relay.