Fuel filter
Traps contamination before it reaches sensitive fuel hardware.
In the fuel line or fuel module, depending on model.
The filter media catches particles; some diesel assemblies also manage separated water or fuel heating.
A sieve protecting a precision spray system.
Restriction can reduce delivery; pressure tests distinguish it from pump and electrical faults.
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.
BMW fuel-filter access and replacement guidance vary by fuel type and vehicle generation.
BMW combustion models; spark components are petrol-only and glow-plug hardware is diesel-only.