I have the same issue, though intermittently, with our similar vintage TC21D. Though I know that fixing the core issue is the right thing to do, I have found the by leaving the tractor in gear (or range on hystat), and turning the key to the start position, the glow plugs will light. Do this for about 10 seconds (starter will not be running because of gear interlock). Then release starter, shift into neutral, and re-engage starter. Should start right up.
