glödstiftet

Glödstiftet, or the glow plug, is a heating element used in compression-ignition engines to preheat the combustion chamber and facilitate starting, especially in cold conditions. The device typically consists of a resistive heating element housed in a metal sheath and protected by ceramic insulation. Materials such as silicon carbide and platinum are commonly used for their high-temperature stability and longevity. In many modern engines, several glow plugs are aligned with the cylinders, and their operation is coordinated by the engine control unit (ECU).

During cold starts, the ECU energizes one or more glow plugs for a controlled period around the cranking process, raising the temperature inside the cylinder to aid ignition. After the engine starts, electrical current is cut off and the plug cools. In indirect-injection engines, glow plugs may heat a prechamber; in direct-injection designs, the need for prolonged heating is reduced, though some systems still provide heat during cold operation.

Failures of a glow plug can manifest as extended cranking, failed starts, white smoke on startup, or rough running. Electrical testing with a multimeter or diagnostic codes can confirm a faulty plug, and replacement should use the correct specification to maintain balance among cylinders. Service life varies with design and operating conditions but is generally substantial, with many vehicles rated for tens of thousands of kilometers of normal use.

Etymology: glöd means glow and stift means pin in Swedish, and glödstiftet is the definite form for “the glow plug.” The term is used in Swedish automotive contexts to refer to this component.