Glow plug in cylinder and in package with washerPhoto © M. James
Why It's Called a Glow Plug: The glow in glow plug is because a filament inside the plug glows when the plug is hot.
Getting a Glow Plug Hot: To get the glow plug hot so that it can ignite the fuel in the engine cylinder you heat it with a battery-powered glow starter or glow plug warmer. Once the engine is running combustion keeps the glow plug hot.
Parts of a Glow Plug: An integral part of the glow plug is the glow plug washer, a tiny copper ring that goes on the glow plug before it is inserted into the engine cylinder.