sometimes won't start on 2001 Ford Explorer

sometimes when I go to start it, i can hear a soft humming of what i think is the fuel pump and the engine starts fine, but sometimes i cant hear that noise, and it won't start. sometimes if i wait a min or two and try it again, maybe after a few tries, eventually it starts. what could be causing this?

1 answer
does it start and stall immediately? if it does you have an idle air control valve problem.the humming noise is a telltale sign of it also.see it alot!!!