Usually the carbureted Lycoming O-320 in my Skyhawk is easy to start.
But when it gets cold (below freezing), often the first crank yields
nothing. Not even a hint of a kick regardless of how long the starter
is engaged. Doesn't matter how many shots of prime are in there either
(in cold weather I normally use 3 or 4). The "trick" I've found that
works is to wait 5-10 seconds after disengaging the starter, NO
additional priming, then engage the starter. Usually starts in two or
three blades. In the rare instances that the engine still isn't
started at this point, I'll add a couple more shots of prime and try
the same sequence again.

Be darned if I know why this (waiting between cranks) works, but it
does. If anyone knows why or even has a theory, I'd love to hear it.
Jim Rosinski