1990 Questions for all other cars Fuel Pump, Relay, Filter?

I got a 1990 Winnebago from a man. It has a Chevy 454 and chevy drivetrain. He got hurt so it sat for a year. He says he started it whenever he could during that time. It started fine and drove fine for a couple miles and then backfired pretty good. The next day it died twice while starting but ran after that. I drove it about 20 miles and then another loud backfire. 5 miles later it died and will not start. The batt. drained as well. I charged the batt. and can get the generator to come on but not the engine. The starter crankes the engine but nothing else happens. I am just starting the search for the problem and am looking for help to speed up the process. thanks