The aircraft was parked on a slope left wing low and had been exposed to rain prior to the flight. The pilot sumped all 4 fuel tanks and then visually determined that he had sufficient fuel for the 1 hour flight to destination. After departing on the right main tank and briefly using both auxiliary tanks, approximately 30 minutes into the flight he switched to the left main tank and the engine began missing. Believing that he had no fuel in the left tank, he switched to the left auxiliary which he exhausted and back to right main which was also exhausted. After a total of 55 minutes of flight and while approaching his destination, he was unable to maintain power on the right auxiliary and executed a forced landing. During the approach he determined that power lines interfered with his landing and maneuvered to an alternate landing site. This maneuver resulted in the pilot's inability to safely flare due to sink rate and low airspeed and a hard landing followed. A total of 5 gallons of fuel was drained from the left main tank subsequent to the forced landing.