At about 1030 Eastern time, the airplane collided with trees during takeoff. Visual conditions prevailed. The airplane was substantially damaged; the commercial pilot and sole occupant sustained minor injuries. The pilot later stated the auxiliary fuel pump was on for takeoff, and during the initial climb, the engine did not seem like it was developing full power. The flight continued past the departure end of the runway, over trees, clipped tops of them, then descended and impacted the ground. Prior to contacting the trees, the fuel pressure gauge was indicating below the green arc. Examination of the wreckage revealed the auxiliary fuel pump switch was in the off position. Power was applied to the auxiliary fuel pump, but it did not operate. When the pump was tapped with a screwdriver handle, clicking sounds were heard. No fuel was noted at the flexible fuel hose connected to the inlet of the auxiliary fuel pump, while fuel was noted at the flexible hose connected to the outlet of the auxiliary fuel pump.