At about 19:30 mountain time, a Piper PA-24-250 suffered fuel exhaustion while on final approach to runway 21R at Love Field and crashed about 450 feet short of the runway. The two occupants, both of whom were flight instructors, suffered minor injuries. The engine failed on approach with the fuel selector was positioned to the right auxiliary fuel tank and the pilot restored power seconds before impact by switching to a main fuel tank. Investigators found about 10 gallons in the left aux fuel tank, 25 gallons in the left main tank and 15 gallons in the right main tank. The right aux tank was completely dry.