The needle valve is pressed against the seat by a spring in the resting state and is opened by an electromagnet and anchor. When a voltage pulse is received from the ECU-KSUD, a magnetic field is created in the electromagnet winding, the anchor is pulled in, the needle valve moves away from the seat and fuel is sprayed under pressure through an annular calibrated gap. The amount of fuel injected depends on the injector open time, which is determined by the ECU-KSUD based on information received from the sensors.
Difficulty starting, failure to start, and unstable engine operation at idle indicate the possibility of injector failure.
Information obtained from this online resource «BMWMAN.ru»