Here's a pic of the glow plug on the front end of the intake manifold.
Supposedly there is a bimetal spring that when heated up (electrically) causes the fuel to leak out and is set on fire. Makes the air in the manifold HOT and causes quicker starts.
This manifold is off a 3600 but all 3 cyl diesels have about the same deal.
If yours doesn't have the glow plug it will have a pipe plug there where you can install one.