2004 4.3 hard to start after sitting for a couple of days

[coody]

truck starts fine every day. Let it sit a couple of days and doesn't want to start. I can hear the pump prime but no start. Turn key on several times to prime maybe loosing prime, but have fuel at pressure tap. Pull plugs they are dry and getting fire to plugs. Pull top off of throttle body put hand over top and crank the motor. started to spit n sputter and started up. This happened before and the crank position sensor was bad. Now it starts and runs fine now.wierd! This has happened a couple of times on me. Any suggestions ?tks