Ether (starting fluid) is OK in some diesels others it's not. It depends on the design of the engine. The combustion chamber of your engine can be one of two designs: Direct Injection or Precombustion chamber.
A Pre-cup engine has a small seperate chamber in the head that the injector fires through and also holds the glow plugs. These chambers can have a thin stamped metal shell or thin casting seperating it from the main combustion chamber. The idea is that the combustion starts in the Pre-cup and that ignites the remaining fuel/air in the cylinder. You see these used on smaller engines: (cars, trucks, small tractors). Ether should not be used on a Pre-cup engine as you can create too much combustion pressure in the small chamber and actually blow-up or blow-out the Pre-cup walls.
Direct injection motors have no Pre-cups and have no glow plugs. Ether is required to start these on really cold mornings. Often there is a factory installed on-board ether injection system operated by a push button on the instrument panel. These are the big diesels; crawlers, excavators, Kenworth trucks, ect.
Glow-plugs mean don't use Ether (unless your REALLY-REALLY careful).
If you diesel car won't start on a cold morning, odds are you have one or more burn't out glowplugs. Check them for continuity. :awesomework: