Fuel injector
Meters fuel into the intake or combustion chamber.
In the intake port or cylinder head, depending on injection type.
The controller commands a valve; pressure, spray design and opening duration affect fuel delivery.
A precisely timed spray nozzle.
Misfire, rough starts or mixture faults may involve leakage, deposits, pressure or wiring.
Plugs and filters use engine-specific service guidance. Pumps and injectors are normally assessed through pressure, leakage and electrical tests.
Spark-plug service is usually less involved than direct-injector or high-pressure-pump replacement; coding and access can add work.
A petrol port injector and a BMW direct injector are different hardware even if both are called injectors.
BMW combustion models; spark components are petrol-only and glow-plug hardware is diesel-only.