Fuel system
An electric fuel pump located inside or near the fuel tank delivers pressurized fuel to the fuel line, which distributes the fuel evenly among all injectors. From the fuel line, fuel is injected into the injector inlet located under the inlet valve. The amount of fuel injected by the injector is precisely determined by the Electronic Control Unit (ECU). When starting the engine, an additional injector, known as a cold start injector (only on L-Jetronic systems and early Motronic systems), provides additional fuel to the intake manifold.
The pressure regulator controls the pressure in the system in accordance with the amount of vacuum in the intake manifold.
The fuel filter between the fuel pump and the fuel line filters the fuel to protect system components.
Air intake system
The air intake system consists of an air filter housing, an air flow meter, a throttle housing, an intake manifold and associated air ducts. The airflow meter sends information to the ECU. These models are equipped with a vane type flow meter. The intake air flow is measured by a potentiometer and the temperature sensor measures the intake air temperature. This information helps the ECU determine the amount of fuel injected by the injectors (injection duration). The throttle body inside the throttle body is controlled by the driver. When the throttle valve opens, the amount of air passing through the system increases, the potentiometer signal increases and the ECU controls the injectors to increase the amount of fuel supplied to the intakes.
Electronic control system
The processor control system controls the fuel and other systems through the Electronic Control Unit (ECU). The ECU receives signals from a variety of information sensors that monitor changing parameters such as intake air volume, intake air temperature, coolant temperature, engine speed, acceleration/deceleration, and exhaust oxygen content. These signals help the ECU determine the injection duration needed to achieve the optimum air/fuel ratio. These sensors and their corresponding ECU controlled actuators are located throughout the engine compartment. For further information regarding the ECU and its interaction with the electrical systems of the engine and the ignition system, refer to Chapters Ignition system and Engine management and emission control systems.
Either the L-Jetronic or Motronic system is used. Later models are equipped with a modern version of the original Motronic system.