Stored 1993 S420 has fuel problems-Gives sudden starting problems-solution needed

My 1993 S420 has been stored in the winter since the winter of 2001-2. Has gone only 34K miles.
Used to start and run fine in spring in 2002 and 2003 but in spring 2004 started having a sudden starting problem. Usually after a 15 min drive, it would not start when started again. After repeated starting attempts, it would start once again. This has happened twice. During the starting attempts the car would backfire with a fuel smell. I think the problem has to do with the fuel system and gas in the fuel system, over the winter, clogging up the fuel system.
2004-5 winter I put in some fuel stablizer "sta-bil" and have liberally put in fuel injector cleaner.
After the two episodes in spring 2004 I was afraid to use this car for fear it might not start suddenly.
Any ideas?
Thanks
Kris