Unlike the K/KE-Jetronic system, Mono-Jetronic has a single injection valve, which is located in the center above the throttle valve. The injection valve has electromagnetic control in time with the ignition pulses.
Fuel is supplied by the electric and main pumps located in the fuel tank through the fuel filter to the injection valve. The pressure regulator maintains the pressure in the fuel system constant at 1 bar, regardless of the amount of fuel injected.
Air is sucked into the engine through the air filter and the throttle valve. The angle of rotation of the throttle valve is recorded by a potentiometer and serves as a measure of the sucked air for the control device together with the number of revolutions.
The control unit regulates the injection duration and thus the amount of fuel injected in accordance with the measured amount of air.
When the injection valve is opened longer, more fuel is injected. Additional sensors are used to correctly determine the amount of fuel in different engine operating modes.
The throttle end position sensor switch is located directly on the throttle shaft. It informs the control unit of the idle position. The control unit automatically sets the required speed, and the throttle valve is closed or opened accordingly by the motor. This ensures a more stable and low idle speed, regardless of engine temperature.
The temperature sensor on the cooling system pipe measures the engine temperature, which has a major impact on fuel consumption.
The intake manifold temperature sensor measures the air temperature. The intake air temperature is taken into account by the control unit to determine the mixture quality.
The intake air heating device on a carburetor engine prevents fuel condensation in the intake manifold.
Lambda probe (oxygen sensor) measures the oxygen content in the exhaust gases and sends a corresponding voltage signal to the control unit. Based on this, the control unit changes the fuel/air ratio so that the level of toxic substances in the exhaust gases is kept constant at the lowest level.
The Mono-Jetronic system is virtually maintenance-free, with only the air filter element having to be changed every 30,000 km.
1 - control device
2 - connection plug. For the throttle valve controller and idle switch sensor.
3 - throttle damper
4 - connection plug. For injection valve and intake air temperature sensor.
5 - throttle valve regulator with idle speed switch sensor
6 - injection valve and intake air temperature sensor
7 - fuel pressure regulator
8 - intake silencer
9 - valve for controlling the vacuum regulator of the ignition moment
10 - injection unit
11 - throttle potentiometer
12 - water deflector. For throttle potentiometer
13 - Engine electronics control lamp. On the dashboard there is a diagnostic connector: up to 7.88 fuel pump relay, from 8.88 to 7.90 driver's side footwell
14 - Lambda probe plug
15 - Magnetic valve I, grey. For activated carbon box.
16 - Magnetic valve II, black. For activated carbon box
17 - coolant temperature sensor
18 - thermal switch, red, intake air heating
Upper part of the injection unit
1 - bolt, 5 Nm
2 - injection valve holder. With intake air temperature sensor. Measure the resistance of the sensor between the outer terminals of plug "18".
3 - cap. Only for transporting spare parts, remove when installing
4 - O-ring seal. Always replace
5 - injection valve
6 - bolt, 6 Nm. Cover the thread with protective agents D6
7 - upper part of the injection unit
8 - gaskets. Replace if damaged
9 - bolt, 3 Nm
10 - holder
11 - lid
12 - spring
13 - membrane
14 - pressure regulator
15 - bolt, 6 Nm. Cover the thread with protective agent D6
16 - threaded nipple
17 - gasket
18 - plug. To remove, unclip the clamp
Bottom part
1 - Stop bolt. For the throttle valve. The bolt is fixed at the factory and cannot be rotated
2 - circular section seal
3 - cork
4 - bolt, 3 Nm
5 - holder
6 - connecting pipe
7 - connecting pipe
8 - throttle potentiometer
9 - lower part of the injection unit
10 - water deflector
11 - bolt, 6 Nm
12 - throttle valve regulator. For stabilizing idle speed. Can be activated only through the polymer plate with the stop bolt "13". If necessary, loosen and align the holder "15".
13 - stop bolt. For the throttle position control sensor-switch "17".
14 - throttle damper
15 - holder
16 - protective sleeve
17 - throttle position sensor-switch. For stabilizing idle speed, vacuum adjustment of ignition, deviation of fuel supply of forced idle speed.
18 - bolt, 6 Nm