Fuel Injection System

GENERAL INFORMATION

All models with single-point fuel injection are equipped with a combined fuel injection/ignition system (engine management system), often referred to as ECCS (Electronic Concentrated Control System). The fuel injection system operates as follows.

The fuel pump, installed in the fuel tank, pumps fuel from the fuel tank to the throttle body through a filter mounted on the rear wall of the engine compartment. Fuel pump pressure is controlled by the pressure regulator, which is mounted on the side of the throttle body. The pressure regulator opens so that excess fuel can return to the fuel tank when fuel system pressure exceeds the optimum level. To reduce exhaust emissions and improve drivability with a cold engine, an electric heating element is installed between the throttle body and the intake manifold to quickly warm up the throttle body during cold engine starts.

The electronic engine management system consists of an electronic control unit (ECU) and the following sensors: – throttle potentiometer – informs the ECU of the throttle valve position and the closing/opening speed of the throttle valve; – coolant temperature sensor – informs the ECU of the engine temperature; – air flow sensor – informs the ECU of the quantity and temperature of the air entering the throttle body; – crankshaft angle sensor (installed in the ignition distributor) – informs the ECU of engine speed and crankshaft position; – vehicle speed sensor (installed in the speedometer) – informs the ECU of the vehicle speed; – power steering switch and air conditioning switch – inform the ECU when these systems are switched on, so that the ECU can adjust the engine idle speed to compensate for the additional load on the engine from these systems; – exhaust gas sensor (only on models with a catalytic converter) – sends information to the ECU about the oxygen content in the exhaust gases.

The ECU analyses the signals from all of these sensors. Based on this information, the ECU controls the fuel injector operation (by changing the pulse duration – the period of time during which the injector is open) to produce a richer or leaner fuel mixture, as required. The fuel mixture composition and engine idle speed are constantly adjusted by the ECU to ensure optimum engine starting (cold or hot start), engine warm-up, engine idling, best engine performance during highway driving and during rapid acceleration.

The ECU also fully controls engine idle speed through the auxiliary air valve. This valve, which is installed on the throttle body, controls the opening of the air passage that bypasses the throttle valve. When the throttle valve is closed, the ECU controls the opening of the valve, which regulates the amount of air passing through the throttle body bypass passage, and thus controls the engine idle speed.

The throttle body has a device that can automatically increase the engine idle speed while the engine is warming up. This function is controlled by a thermo-valve. When the engine is cold, the wax capsule in the valve is small (the valve is installed in the throttle body), and the fast idle cam holds the throttle valve slightly open. As the engine warms up, the wax capsule expands, raising the valve plunger, which in turn rotates the fast idle cam to the required position. In addition, a solenoid valve for increasing engine idle speed is installed on the throttle body, controlled by the ECU. The solenoid valve controls the opening of the air passage that bypasses the throttle valve and is used to increase engine speed when the power steering system or air conditioner is switched on.

On models with a catalytic converter, described in subsection 6.4.1 and subsection 6.4.2, the ECU also monitors the exhaust emission control system and the evaporative emission control system. If the signals received by the ECU from the sensors go beyond the permissible limits or do not agree with each other, the ECU switches to fail-safe mode. In this case, the ECU ignores the incorrect sensor signals and uses a predefined value in place of the sensor signal, which allows the engine to run, although with reduced efficiency. If the ECU switches to fail-safe mode, the warning lamp on the instrument panel illuminates and the corresponding fault code is stored in the ECU memory.

If the warning lamp illuminates, have the vehicle inspected by a specialist as soon as possible. A full diagnosis of the engine management system can be carried out at a repair shop using electronic diagnostic equipment, which is simply connected to the diagnostic connector. Warning The engine ECU also has a self-diagnosis mode that can be used by the vehicle owner (see subsection 6.3.1.12).