jeffie8696; Thank you for the suggestions! Cam timing is correct, and the glow plug is an OS F. The valves might be on the loose side, but I'm not sure. A .0015" feeler gauge will pass freely, a .004" will pass with some friction. I set the valve clearances yesterday before I ran the engine. The valves seem to seal better after I adjusted them.

I'll try a fresh bottle of fuel and see if that changes anything.