01 Expy cranks, won't start when cold

[mvigil00]

I have a 01 Expedition EB 5.4. Just a few days ago it didn't want to start. It cranks fine just won't start. Yesterday the weather warmed up a bit and it started fine. This morning, again it didn't start. At about 1pm when it warmed up again, it fired up fine. Obviously something about the cold temperature is causing this problem. Any suggestions as to what might be causing this problem?