Glow plugs have two functions—get the engine started and keep it running. By passing a low voltage electric current through the plug's wire element, a high temperature orange-white glow is produced; this allows the engine to be started when the proper mixture of fuel and air is present within the combustion chamber. After starting, the source of the electric current is removed from the plug … but it continues to glow, keeping the engine running.

A glow plug works by a combination of catalytic action, compressive heating, and the ability to retain a portion of its heat from cycle to cycle. First, the platinum alloy coil of wire within the plug's cavity heats-up as it comes in contact with the fuel's methyl alcohol vapor; this is a heat releasing catalytic action. Next, the temperature of the plug's wire element is further increased by the engine's compression of the air-fuel mixture. This increase in temperature allows for the ignition of the second componenet of the fuel mixture, the nitro methane. Without this 2 stage ignition process, glow engines would be incapable of producing any power ( if ran on methyl alcohol alone) , or would run too hot for the materials that the engine is constructed from ( if running nitro methane alone ). Manufacturers produce glow plugs in various heat ranges: hot, medium, and cold. Many factors determine the heat range, but it's important to note that hot plugs advance the ignition point timing, while cold plugs retard it.

Gasoline will ignite at 536f ( 280c ). Methyl alcohol will not ignite until it reaches 725f (385c). The Nitro Methane in glow fuel will not ignite until it reaches 800f ( 427c )!

By the nature of a glow plug, the gasoline vapor would detonate on contact with the super heated glow plug. The resulting uncontrolled explosion would destroy the motor, and probably injure or kill anyone standing around.

DO NOT EVER USE GASOLINE IN A GLOW POWERED ENGINE! EVER!