How can I fix my Cub Cadet LT1018 lawn tractor?

M LT 1018 has 340 hrs. and has always run great but in the last couple of weeks it will suddenly die. Sometimes It will run for hours, sometimes 20-45 min. I could usualy restart it with a little trouble, but a lot of times it would start, then die right away for a while, then it would run fine the rest of the day. I changed all filters, cleaned and re-gapped the plug, made sure it has clean gas. Now it ran great for 30 min, died and wont start at all. It fired a little, but now all I do is run down the battery. Could it be the the fuel pump?