You’ve got a problem of some kind or another in the car’s evap system. There’s various gadgets involved that can fail, something as simple as a split or disconnected hose to more complicated, like a purge or vent solenoid or even a faulty fuel tank ass’y. There’s also various sensors and air or vacuum pumps. It seems like the purge valve is one of the most common failures reported here. The simplest way to fix it, you’ll need to get the car to a shop that specializes in Chrysler products for a proper diagnostic. Once you get the diagnosis, you can decide if you want to do the work yourself or not.
http://www.agcoauto.com/content/news/p2_articleid/295
http://www.agcoauto.com/content/news/p2_articleid/294