Bosch Mono-Jetronic A2.2 system
The Mono-Jetronic A2.2 system is a single-point fuel injection system incorporating a catalytic converter in the exhaust system.

The fuel pump, located in the fuel tank, pumps the fuel through a filter to the single fuel injector. The electronic control unit (ECU), which is triggered by the ignition circuit, sends impulses to the injector, which sprays fuel upstream of the throttle valve. A constant fuel pressure is maintained by a fuel pressure regulator, which returns excess fuel to the fuel tank. The ECU also receives information from various sensors to determine engine temperature, speed and load, and the quality of air entering the engine. The sensors inform the ECU of throttle position, inlet air temperature, coolant temperature, and exhaust gas oxygen content. Engine speed and crankshaft position information is provided by the ignition circuit. All the information supplied to the ECU is computed and compared with pre-set values stored in the ECU memory, to determine the required period of injection. The injector operates four times per engine cycle, and the injector opening duration is varied to control the quantity of fuel delivered.

The ECU constantly varies the fuel mixture and engine idle speed to provide optimum engine efficiency under all operating conditions, and to reduce exhaust gas emissions. The mixture strength is accurately controlled to maintain it within the operating limits of the catalytic converter.

MMFD Mono-point G5 and G6 systems
The Mono-point G5 and G6 systems are single-point fuel injection systems also incorporating a catalytic converter in the exhaust system. The only difference between the two systems is that the idle speed is controlled via a control valve on the G5 system, and via a control motor on the G6 system. The system operation is as described above for the Mono-Jetronic system and is under the overall control of an electronic control until (ECU), which also controls the ignition system.