Glow Plugs - How to Manuall Glow

The factory glow plug timer will be active for ~15 sec, then switch off. Sometimes this is not enough time. To manually activate the glow plugs, turn the key slightly past ‘run’ towards ‘start’. You should hear the glow plug relay activate with a soft click, and the volt meter drop. You can also do this once the engine is running, to help it warm up faster on very cold mornings.

Refer instructional video http://www.youtube.com/watch?v=ihF0H_TXiwo

You may also want to refer to the wiki page on Glow Plugs.