I've run into a little problem. My 6.2 won't start, actually, it won't even turn over. It's not the batteries, I've checked them. Glow plugs heat just fine. When I turn the key, it acts like a dead battery, but the voltage on the meter doesn't drop, even like it does during a normal start. I can hear the starter engage the flywheel, but that's it. The engine doesn't even start to turn. Do these things ever get vapor locked? Has anyone encountered this before? Any suggestions?