Ford Escort stalling and refusing to start for hours.

This is an 87 Ford Escort with 38,000 miles on it. It has been sitting for about 2 years, but I was told it had this problem before that. When I turn the ignition to "on" I can hear buzzing in the back for about a second, I was told this is the fuel pump, and that means its working. If I havent tried to start the car in about 4 hours, it starts right up with no fuss, and will idle for seemingly random amounts of time. Sometimes 30 mins, sometimes 5. I just replaced the radiator fluid. The temp gauge on the dash doesnt get very high at all, still at the bottom of the "normal" range. I put a little fuel injector cleaner in the gas, didnt help. Any ideas? Need any more information from me? Any help is greatly appreciated. I dont want to buy a fuel pump unless im absolutely positive that is the problem, because thats some expensive buisness. Oh also I tried the fuel pump reset switch, but it wasnt tripped.