My problem WAS after driving for a short time, car would stall and would not start, but after waiting for it to cool down, it would start again. I got a code PO340 and replaced the camshaft position sensor. The problem still existed. The next morning I got a new problem, It cranks and won't start. I replaced the crankshaft positioning sensor. Still won't start, only crank. I then proceeded to check out my fuel pump. Fuse and relay are OK. I also hear the hummmm at the fuel pump. I don't know what to check or replace next. Any help will be greatly appreciated. It's a 2002 Altima SE 3.5

Are you getting spark and are you getting fuel to the injectors? Just because the pump is working doesn't mean the injectors are. I would check for spark first as it's the easiest of the two.