I had a '77 Ranchero that had a similar problem. I found that when cold I could crank and crank the engine and it wouldn't start. The funny thing is that after I let go of the key it would start. It was the wierdest thing and turned out to be the selenoid. When cold and the key was in the start position, the ignition wasn't getting electricity; but it would when the key was released and went to the run position. Fortunately, the engine was still moving and would get spark and start.

Wierd!!!

Bruce