My ElCo did EXACTLY the same thing when I got it. I could dump a bit of gas down the carb and all was good for the day. If it sat overnight looooooooong cranking and pedal pumping would finally start it. The carb would leak down and be empty overnight. After a little research, I decided I didn't want to play with a computer controlled carb. Decided if I'm gonna have a computer might as well upgrade to an LS!I've got a good idea what needs to be done but some of you know alot more. All the smog stuff was removed and dual exhaust with no cats or 02 sensors was added by the previous owner. In his infinite wisdom he left intact the electronic Quadra jet and distributor. The ECM is now confused. (Limp mode I suspect) For the past year I've been able to start it if it didn't sit for long. After a week or so it would take a few pumps of the pedal and then start. At this point it sat for a little too long and will not start. I'm thinking the carb is no longer willing to cooperate and it's time to replace it as well as the distributor. Or could it simply be the fuel pump? All input is welcome but please no lectures my wife has already taken care of that. Thanks in advance.
You might have multiple problems though and 57's suggestions are right on!