My 04 Kia Sedona cranks but doesn't start up?

Changing the crank sensor is a guess.
It may be the problem, but throwing parts at it can be expensive.
First, verify if you have spark and/or fuel, then go from there.

You should have the check engine light on--rent a scanner, read any codes, and pursue to repairs. Don't just start replacing parts on someone's suggestion--it can get very expensive. It could be either the crankshaft or camshaft sensor, but it could also be a problem in the fuel or ignition system or a timing belt problem (if this is an overhead camshaft engine). Good luck!