Air in the lines or a heat issue?

[byronnash]

Went to crank up the 84 300TD today and it wouldn't turn over. It was parked on a hill nose up so I'm thinking it may have gotten some air in the lines. How can I tell if it's that or glow plugs acting up? I don't have a lot of time to diagnose since I need to drive it tomorrow morning. The last time I had some cranking issues it was heat related and would end up turning over after a while. This time I can't get it to go and there does not seem to be smoke.

Am I right to try the lines first?