Two teen-agers who were burned when gasoline fumes exploded in the garage of a Carson home were rescued by a Los Angeles County sheriff's deputy who was in the neighborhood to investigate a burglary. Deputy Brian Schlosser, 30, ran to the Radlett Avenue house when he heard a muffled explosion and saw smoke pour from the garage. Jerome Mangram, 18, and Dorell Potts, 14, staggered from the burning garage when Schlosser opened the door. Schlosser, who said he was a firefighter for three years before becoming a deputy, extinguished the flames with a garden hose. The youths were treated for burns and smoke inhalation at Harbor-UCLA Medical Center. Deputies said fumes from gasoline used by the youths to clean oil spots from the garage floor were ignited by a clothes dryer's pilot light. Damage was set at $5,000.