I have a Briggs/Straton 22hp v-twin and it has become hard to start?

I own a John Deere L120 with a B/S v-twin OHV engine. It has become very hard to start , Freash tune up 150 hours. When it sits for a few days, my wife runs the battery down trying to start. I've noticed that the clear filter is dry. Do I have a bad fuel pump which will allow the gas to return to the tank. I'm ready to install a out board primer bulb. Befor I go to the extreme can I overhaul the fuel pump, and verify that a check valve is hung in the open position at all tims allowing the gas to flow back?