[moose07]

It’s a glow-plug.
Diesel engines don’t use spark plugs.
The fuel is ignited by compression induced heat.
During the start-up and early running of the engine there isn’t enough heat to run the engine so these little beauties glow white hot to start with then red hot after the engine starts. They turn off after 20 mins, as the cylinder head is hot enough to sustain the ignition process using compression alone, at 21:1 ratio.

Neither of those two have enough energy to spark, and could only glow in an emergency. Possably. :)

[The Cajun]

Moose07 do know the way of the diesel, I'm impressed!

[RedMDer]

Neither of those two have enough energy to spark, and could only glow in an emergency. Possably. :)
ROFLOL!