The fuel pump is located in the fuel tank. It is switched on and off by means of a relay and conveys the fuel via the fuel filter and pressure regulator to the fuel distributor.
The DME control unit can only monitor activation of the relay but not of the pump itself. The relay is activated via a safety circuit only when the engine is running. The relay is also briefly activated after switching on the ignition (ignition lock position 2) for the purpose of building up the pressure in the fuel system. The DME control unit will interrupt activation of the relay if the engine is not started.
The DME control unit will switch off the relay immediately if no longer detects engine speed. This ensures that the fuel pump cannot continue running when the engine turned off.