Diesel glow plug
Adds local heat to help a diesel engine’s combustion conditions.
Threaded into a diesel cylinder head.
The heater supports cold starting and other controlled operating phases; it does not spark like a petrol plug.
A small electric heater in the combustion area.
Cold-start roughness or glow-system faults can involve plugs, wiring or the controller.
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 BMW diesel’s glow system is controlled; forcing power directly to an unknown plug is not a diagnostic method.
BMW diesel engines equipped with a controlled glow system. Not a substitute for petrol spark plugs.