Volatility ( even if by thermal decomposition ) is the necessary, but not sufficient condition for liquids to be combusted, forming a flame.
Liquid helium is the most volatile liquid ever, but there is no way to burn it ( chemically ).
As other answers mention, there is correlation, as flammable liquids are generally less polar and more volatile than polar and less flamable molecules of similar mass. But there are many exceptions on both sides.
BTW water is volatile as well, more than the diesel fuel.
I am curious, what would you thought there would be the result of water combustion ?