Diesel engines are very sensitive to starters which are operating too slowly. I just ran into this on my 20 year old NY TC33D. I was having hard starting issues - had to crank for an extended period, sometimes had to cycle the glow plugs multiple times. It acted exactly like tyring to start on a tough winter day. When it did start, I'd get some blue smoke for a few seconds, then it would run as well as it ever did. Air filters were fine. Glow plugs operated normally. I feared valve or compression problems.
Turns out, the starter was worn and dragging resulting in slower cranking. It came on so slowly that I did not really notice it. Once the dealer replaced the starter, it started like new. The service tech explained that when starting a diesel engine, cranking speed makes a huge difference. Since here is no spark plug to ignite the fuel/air mixture, it relies on the heat of compression to ignite the mixture. Slower cranking = less heat generated. Less heat = difficult or no start. The puff of blue smoke is from all of the unignited fuel that remained in the cylinders from the extended cranking.