1996 Ford Bronco Hard to start when it rains or sits a few

Truck is difficult to start when it rains and also when it has sat a while usually a couple of days. Once it has been started and has run for a while it will startup with no problems and continue to operate normally as long as the above mentioned to conditions haven't happened. There is also usually a strong smell of gas after several attempts at turning it over. Haven't tried anything as of yet to fix it although the fuel pump has been changed within the last year. Someone suggested changing the distributor cap. Any suggestions would be appreciated.