1996 Sentra wont start.

If you smell fuel, there is a chance that the engine is 'flooded' and fuel has wet the plugs. You can dry it out to some extent by pushing the accelerator slowly to the floor and holding it there while you crank the engine. If it still won't start (or at least fire a couple of times) then you may not have any spark to drown. If it does sputter a little, continue holding the pedal down and continue cranking to see if the other cylinders will follow. It's time to pull a plug wire, place it on the block or other grounded surface and have someone crank it to see if there is any spark at all. If not, there are too many things that could prevent it so you may have to have the computer scanned to see what might have failed.