On June 1, 2013, about 1125 central daylight time, a Cessna TP206B, N3350J, nosed-over and impacted terrain during a forced landing that was short of runway 20 at Door County Cherryland Airport (SUE), Sturgeon Bay, Wisconsin. The airplane experienced a total loss of engine power. The airplane sustained substantial damage. The commercial pilot was uninjured. The airplane was registered to Out of the Blue Skydiving LLC and operated by Skydive Door County under 14 Code of Federal Regulations Part 91 as a skydiving flight that was not operating on a flight plan. Visual meteorological conditions prevailed for the flight that originated from SUE about 1100. The pilot stated that he departed for about a 25-minute flight to drop parachute jumpers above SUE. In-flight fuel management was through the use of the airplane fuel selector that drew fuel from either the right or the left fuel tank. He said that he was instructed during his airplane checkout that the fuel tanks cross feed like other high-wing Cessna airplanes that he was familiar with, and he did not recall anything that was contrary to that within the pilot operating handbook. There was about 22 gallons of fuel on board, which would have been enough for the flight. He said that he was advised that the entire flight could be flown from the right fuel tank only due to continuous banking. The pilot stated that he took off and climbed using the left fuel tank, which had 5 more gallons of fuel than the right fuel tank. About 6,500 feet mean sea level, the engine stopped. While turning back toward SUE, he switched fuel tanks because the right fuel tank indicated a greater fuel quantity. The engine restarted about 20-30 seconds after he switched to the right fuel tank, and the engine continued to operate during the return and climb over the drop zone. After dropping the jumpers, he slowly reduced engine power and spiraled down for landing. He performed a final [gas, undercarriage, mixture, and propeller] check for landing and selected the left fuel tank, which indicated a greater fuel quantity. The engine ran for about 60 seconds after the left fuel tank was selected and then it quit while the airplane was on a base leg about 1-1.5 miles from runway 20 (4,600 feet by 75 feet, asphalt). The pilot stated that he read the POH [Pilot Operating Handbook], and he did not recall anything about the fuel system being cross-fed. He stated the he may not have read it as detailed, because he was told the fuel system was cross-fed. The 1967 Cessna Super Skylane Owner's Manual, Fuel System, states, in part: "Fuel from each wing tank flows through a fuel reservoir tank to the fuel selector valve. Depending upon the setting of the selector valve, fuel from the left or right tank flows through a fuel strainer and by-pass in the electric auxiliary fuel pump (when it is not operating) to the engine-driven fuel pump. From here fuel is distributed to the engine cylinders to the engine cylinders via a fuel control unit and manifold. "NOTE Fuel cannot be used from both fuel tanks simultaneously." "Vapor and excess fuel from the engine-driven fuel pump and fuel control unit are returned by way of the selector valve to the reservoir tank of the wing tank system being used." Figure 2-2 provides a fuel system schematic. Examination of the airplane by a Federal Aviation Administration inspector from the Milwaukee Flight Standards District Office revealed that the right fuel tank vent system was unobstructed. The left fuel tank vent system was obstructed with an unknown substance.