My TORO + Loader has a separate glow plug switch. When I start it in cold weather, I hold the switch on after it starts, until it runs smooth. Been doing it for ten years, you can see the current draw on the ammeter, so I know they are working.
My 2006 GMC Duramax has an indicator that goes out when it is OK to start, but by looking at the voltmeter, the glow plugs are still on. After it starts they stay on quite awhile, then they cycle off on back on while driving for several miles, if it is real cold.