On September 10, 2000, at 1815 eastern daylight time, a Grumman AA-5A, N26934, collided with the ground during a forced landing at the St. Augustine Airport in St. Augustine, Florida. The personal flight was operated under the provisions of Title 14 CFR Part 91 with no flight plan filed. Visual weather conditions prevailed at the time of the accident. The airplane sustained substantial damage. The private pilot and her two passengers received serious injuries. The accident occurred during the takeoff from St. Augustine, Florida, at 1814. The private pilot reported that the engine sputtered shortly after takeoff from runway 13 as the airplane climbed through 100 feet. The pilot then stated that she switched the fuel selector from the right tank to the left tank. The pilot reported a complete loss of engine power. The pilot elected to make a forced landing on the remaining runway. The airplane subsequently collided with the runway during touchdown, and skidded off the runway. The airplane came to rest in a marshy area several hundred feet left of the runway centerline. Examination of the airframe and the engine assembly failed to disclose a mechanical malfunction or component failure. During the subsequent examination, necessary repairs were made to the engine assembly to facilitate a functional check. The engine operated normally up to 2100 rpm during the functional check. The post-crash examination of the airplane also revealed evidence of rust and water in the fuel boost pump.