Bosch Mono-Motronic Engine Management System Diagram
1. Fuel filter; 2. Fuel tank filler neck; 3. Equalizing tank; 4. Fuel tank with electric pump; 5. Activated carbon filter; 6. Fuel vapor recirculation solenoid valve; 7. Throttle position sensor; 8. Coolant temperature sensor; 9. Lambda sensor; 10. Crankshaft position and speed sensor; 11. Intake air temperature regulator; 12. Fuel (nozzle; 13. Idle code frequency regulator; 14. Diagnostic connector; 15. Fuse; 16. Fuel pump relay; 17. Electronic control unit; 18. Ignition coil with amplifier; 19. Catalytic converter; 20. Battery.
Bosch Mono-Motronic system - engine management system that controls fuel injection and ignition (see illustration). This Section describes only the components of the fuel injection system - information about the components of the ignition system see Section 5.
The fuel injection system includes a fuel tank, an electric fuel pump, a fuel filter, fuel supply and return lines, a throttle body with an integrated electric fuel injector, and an electronic control unit (ECU) along with associated sensors, actuators and wiring,
The fuel pump supplies fuel through the filter to the throttle body, under pressure slightly higher than required - the fuel pressure regulator is mounted in the throttle body and maintains the fuel pressure in the injector at a constant level, returning excess fuel to the tank through the return pipe. Due to the constant circulation of the fuel, its temperature decreases and evaporation is prevented. The fuel injector is opened and closed by an electronic control unit (ECU) that calculates injection timing and duration based on information about engine speed, throttle position and opening, inlet air temperature, coolant temperature, vehicle speed and the amount of oxygen in the exhaust gas received from sensors mounted on the engine.
Inlet air enters the engine through an air filter containing a replaceable paper filter element. The temperature of the inlet air is controlled by a vacuum-controlled valve mounted in the air filter inlet duct, which mixes cool air with hot air coming from the heater on the exhaust manifold. The vacuum supplied to the valve is controlled by a temperature sensor mounted in the air filter.
The temperature of the air entering the throttle body is measured by a sensor mounted directly above the injector. This information is used by the ECU to accurately dose fuel based on temperature. Idle speed control is achieved partly by an electric throttle valve mounted on the side of the throttle body and partly by the ignition system, which adjusts the idle speed by changing the ignition timing. As a result, manual idle speed adjustment is not required.
The oxygen content of the exhaust gas is constantly monitored by the ECU via a Lambda sensor, which is installed in the exhaust pipe. The ECU then uses this information to vary the injection timing and duration, thereby maintaining the optimum air-fuel mixture ratio - as a result, manual adjustment of the CO content in idle mode is not required. All models considered in this Section are equipped with a catalytic converter.
In addition, the ECU controls the operation of the carbon canister of the fuel vapor absorption system.
It should also be noted that it is only possible to detect faults in the Bosch Mono-Motronic system with special testing equipment. Therefore, if problems arise with the system, contact your dealer. Once the damage has been identified, the corresponding component can be replaced (the removal/installation sequences are described in the following Chapters).