sat to long won't start

97 mustang sat for three years and now it wont start, besides a dead batter why would that happen? any tips on how to fix it myself,

thanks

It might require a complete fuel system rebuild. Gasoline starts turning into sludgy varnish after about 3 months. After three years I would imagine its pretty much about the consistency of grade A honey.

Tank boiled out, injectors rebuilt, new fuel pump, new lines... all possibilities.