glow plugs are only for old indirect injection Diesel engines, you have to turn on the ignition before you start the engine, a light appears on the speedo telling you that the plugs are pre-glowing.

thats crucial for starting Diesel engines at low enviroment temperatures....the octane numbers of the Diesel fuel is also important, there is winter Diesel that will ignite better at low temps.

The G-Class Mercedes vehicles of the Bundeswehr (Type WOLF) are very nitpicking with this, mostly they won't start before that light hasn't disappeared, but those are very old non turbo diesel engines (slow as fugg, some vehicles of the KSK special forces and Electronic Warfares have modern direct injecting engines)

modern direct injecting Diesel engines (of course coming from Germany ) don't need pre glowing times anymore, you can start them like any other car, they don't have glow plugs.

check Wiki for explanation why.


besides, Diesel engines are self igniting, so glow plugs aren't = spark plugs.

EDIT:

cool, English Wiki page also shows that "wait to start" sign on the speedo http://en.wikipedia.org/wiki/Glowplug