There are two types of the glow plugs in view of the construction, coil type where the heating coil is exposed, and sheathed type where the coil is protected by the heat resistance pipe (sheath). The coil type was the main by the 1970s but the sheath type is now the most popular taken over all other types of glow plugs. The sheath type glow plug is divided into four groups for the heating time as follows.


Standard Type 20-25 sec to 800℃

The resistance of the heating coil does not vary from temperature, and the glow plug draws the constant current.


Quick Type 15-20 sec to 800℃

The coil resistance increases as the temperature goes up, and the current is almost double of the nominal current when the glow is engaged, and it is possible to heat up quickly.

Q.G.S Type 10 sec to 900℃

The electronics controller and relays control the engaged time and current draw for the quick starting, and also stable running of engine and reduction of smoke at crank.

S.Q Type Max 10 sec to 800℃

While a heating coil and a self-regulating coil be mixed in agreement, it will result in an excellent response to the system simple and quick start.



(1)  Obey the manufacturer’s instructions for the battery capacity because the diesel engine consumes more electricity than the gasoline engine at the starting time. Insufficiency of the battery capacity may not heat the glow plug sufficiently resulting in difficulty of starting. If the battery is deteriorated, the same phenomenon will occur.

(2)  It takes about 25 seconds, 20 seconds, 10 seconds, under 10 seconds and 20 seconds for the standard type, quick type, Q.G.S type and coil type respectively to be heated up. When it does not start excellently after preliminary heating, continuous feeding of electricity may consume battery power considerably and gives an unfavorable influence upon the service lite of the glow plug. Turn the switch to off after preliminary heating and turn on again.


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