A P28 lost power after takeoff because a fuel line leak near the left wing sump allowed fuel to be sucked out of the line starving the engine of fuel.

Narrative

Following a normal preflight inspection; taxi; and run-up; I was cleared for takeoff. The takeoff roll was normal. At or slightly after rotation; the engine momentarily hesitated; then resumed normal function. At approximately 100 FT; the engine began running very roughly and producing about 15 percent of the expected power. Further climb was impossible. I declared an emergency and announced my intention to land; landing was uneventful. Time from declaring an emergency to landing was approximately 30 seconds. Post-flight inspection revealed a large (approximately 8 feet long) fuel stain on the left side of the aircraft; on both the left wing and fuselage. Fuel was dripping from the gascolator fuel sump petcock. I suspect that the fuel line near the drain; or the drain itself; suffered a failure. As airspeed increased; the Bernoulli effect overcame the engine fuel pump's ability; and caused loss of power through fuel starvation. I routinely brief for engine failure in takeoff. At this airport; my procedure is to land on the remaining runway if possible; otherwise the other runway; otherwise generally ahead. I firmly believe that briefing this emergency procedure prior to takeoff contributed to the positive outcome of this event.