My 1998 Saturn SC2 with 118,000 miles has trouble starting up. It seems as if the gas is having trouble flowing. Whenever I allow the vehicle to sit for more than 30 minutes it takes several tries to get the car to run without stopping. Also, after more than 6 hours the car emits a large cloud of white/gray smoke from the exhaust pipe. Could this be an oil leak or should i replace the fuel pump/filter/PCV valve?