2000 Ford Expedition cranks, wont start any idea why? Can it be the timing belt?

I was driving and it turned off on me. I started it and just cranked but no start. It shows low oil pressure. It has gas. And what do you mean if it has gas.

Can you hear the fuel pump come on for 2-3 seconds when the key is turned to on,not cranking? Every time the key is turned to on,the fuel pump will humm/prime for a couple seconds and then it cuts off.there is also an inertia switch(fuel pump cut off switch)in case you're in an accident,get bumped,hit a pot hole,it will trip and cut the power off to the fuel pump in case of a fire. if that happened,you will have to re-set it by just pushing the red button back down. if the pump is coming on,you need to check the fuel pressure and check for spark.also,how is it showing low oil pressure if the engine doesn't start? the engine has to be running before it shows oil pressure.what I mean't by does it have gas in the tank,sometimes the sender in the tank quits working and it may show you have 1/2 a tank or so,but really it's EMPTY,because the float is not working!