which sensors on the nissan maxima would stop it from starting the engine turns over and just floods out

It's not flooding, that's an archaic term for cars with carburetors. The only way it can flood is bad injectors...but do say that because you smell gasoline? There are so many many reasons to cause a no-start. But replacing the ECU is what I would have done...it needs an OBDII scan. Yes, I realize that's very difficult when you can't get it there. But if somehow, some way you could rent, borrow, a scanner that would at least give us a starting point..(no pun intended)