Informal poll

I was on another forum earlier. I was disagreeing with another person and thought I'd just throw this question out there and see if I'm correct. I had a no start condition on an old, long sitting Mopar. The question is this. A friend says his early 70's Mopar turns over but won't fire. You have ten seconds to guess what it could be and with no other information. What would you throw out as your first guess?