AFTER ABOUT 1 HOUR AND THIRTY MINUTES OF FLIGHT, A TOTAL LOSS OF POWER OCCURRED IN THE LEFT ENGINE. WHILE THE PILOT WAS DIAGNOSING THE PROBLEM, THE RIGHT ENGINE LOST POWER. THE PILOT DID NOT SWITCH THE FUEL TANK SELECTORS TO THE OUTBOARD TANKS, AND EXECUTED AN EMERGENCY LANDING ON THE DESERT TERRAIN. DURING THE LANDING ROLL, THE AIRPLANE COLLIDED WITH A FENCE AND NOSED OVER. AN EXAMINATION DISCLOSED THAT THE OUTBOARD FUEL TANKS CONTAINED FUEL; THE INBOARD FUEL TANKS WERE EMPTY.