Glow plug system

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The control lamp of the glow plug system of a Citroën BX (Series 2) can be seen in the red circle . This indicates the preheating process.

A glow plug system is one of the technical ways to make starting a diesel engine easier. In diesel engines, the combustion process is not initiated by a spark, as is the case with Otto engines , but by spontaneous ignition due to the heat of compression .

In order to be able to start a cold diesel engine , the combustion chamber or the prechamber is preheated by means of glow plugs through which an electric current is passed. In the early decades of diesel engines, the pre-glow lasted quite a long time (“ Rudolf Diesel minute minute”). The glow monitor , a heated wire, or later a control lamp, provided information about the heating level. In the course of further technical development, the preheating time could be reduced significantly.

In the case of diesel engines with direct injection without pre-chambers, pre-heating is only carried out briefly and usually unnoticed by the driver at temperatures below freezing point. The manufacturers have started to carry out the preheating process unnoticed when the ignition key is inserted or the doors are opened. It is often after-glowing with the engine running, in order to B. to improve the exhaust gas values ​​with a cold engine and to reduce the cold start nailing.


  • Peter A. Wellers, Hermann Strobel, Erich Auch-Schwelk: Vehicle technology expertise. 5th edition, Holland + Josenhans Verlag, Stuttgart 1997, ISBN 3-7782-3520-6 .
  • Kurt-Jürgen Berger, Michael Braunheim, Eckhard Brennecke: Technology automotive engineering. 1st edition, Verlag Gehlen, Bad Homburg vor der Höhe 2000, ISBN 3-441-92250-6 .

Individual evidence

  1. Deutsche Handwerkszeitung from November 25, 2014: Diesel engines: Pre-glowing in secret. Retrieved February 6, 2015 .