On March 28, 1996, at 1040 Pacific standard time, a Navion, N4826K, registered to and operated by the pilot as a 14 CFR Part 91 personal flight, experienced a loss of engine power shortly after takeoff from the Crest Airpark Airport, Kent, Washington. During the forced landing back to the runway, the nose gear collapsed. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane was substantially damaged and the private pilot, the sole occupant, was not injured. During an interview and subsequent written statement, the pilot reported that he had been doing maintenance on the airplane, and that there was a problem with fuel pressure. The pilot stated that he had removed the fuel pump for inspection and then had reinstalled the pump, however, the problem continued. The pilot stated that prior to additional maintenance, he decided to fly the airplane. Shortly after takeoff, the engine experienced a partial loss of power and the pilot made a 180 degree turn to return to the runway. The pilot stated that he utilized the boost pump to keep the engine running. The pilot stated that just prior to the airplane touching down, he extended the landing gear, however, the landing gear was not fully down and locked at the time of touchdown. The main landing gear remained extended for the landing roll, however, the nose gear collapsed. After the accident, the engine was test run. The engine was hard to start, however, it ran at a low power setting before the throttle linkage broke. After the linkage was repaired, the engine was started again. At 2600 rpm, the engine ran rough and eventually lost power when the rpm was reduced to 2000 rpm. Inspection of the fuel lines revealed a loose fitting on the fuel line running into the electric boost pump. It appeared that the fitting had been loose and leaking fuel for some time. After the fitting was tightened, the fuel pressure increased and the engine ran smooth. Maintenance records indicate that the last annual inspection performed on the airplane was on June 12, 1981. The airplane had accumulated a total of 102 hours since the last inspection.