I just started working on a 84 Starship Berlinetta Camaro. It has a new battery but only cranks and runs on starting fluid.
It has been in storage for 18 years.

 

Pick an end, any end, the front of the car or the back, your choice.......

Now, From whatever end you decided to pick, completely disassemble the fuel system, and clean or replace anything and everything that has fuel that has turned back into the dinosaurs from which it came. After 18 years, it's a pretty good bet that the fuel tank including the pickup, pump and all fuel lines leading to the front, as well as the carb/TBI/whatever fuel induction system is in place, are totally stuffed with the solid gummy, waxy residue of gas that likely went bad about 17 years ago

 

Fuel, Fuel, Fuel!! You will probably be removing the whole rear axle and dropping the tank. If its fuel injected you will be replacing the fuel pump either way you should either clean the tank out which is a pain or buy a new tank. Of course fuel filter. Blow out your fuel lines and spray some carb cleaner down them and blow that out. If its carbureted your float bowls are probably gummy and could be cleaned out might as well do a carb rebuild.