The applied positions of the engine stop pushbutton switch (S11) are read in and evaluated by the MR/PLD control unit. If the engine stop pushbutton switch (S11) is actuated, then irrespective of whether the engine is running or switched off, the MR/PLD control unit interrupts the actuation of the solenoid valves in the unit pumps. The total quantity of fuel delivered by the pump elements to the unit pumps between the bottom and the top dead center, is first pushed into the respective diversion chambers and then into the return flow passage. Since the ejection pressure of the injection nozzles is not reached, there is no injection and the engine switches off and / or cannot be started.
This makes it possible, on the one hand that the engine is stopped and, on the other hand, that in addition to the engine stop pushbutton switch (S10), the engine start pushbutton switch (S11) is also actuated, so that the engine can be turned for service work without it starting.
To avoid switching off the engine accidentally, the engine stop pushbutton switch (S11) must remain pushed until the engine stops. If the engine stop pushbutton switch (S11) is released while the engine speed is over 50 rpm, the engine starts again.