DETROIT—BMW is recalling more than 917,000 older cars and SUVs in the United States—most for a third time—to fix a problem that can cause engine compartment fires. The recall covers many 3 Series, 5 Series, 1 Series, X5, X3, and Z4 vehicles from the 2006 through 2013 model years. Documents posted Wednesday by the U.S. National Highway Traffic Safety Administration say there could be an electrical short in the positive crankcase ventilation valve heater. It can overheat and cause a fire. The fire risk occurs while the vehicles are being driven or soon after they are parked. BMW says the vehicles can still be driven and don’t have to be parked outdoors because fires have been rare. The company wouldn’t comment when asked if fires have spread to any buildings. BMW says in documents that if a driver smells smoke or burning plastic or sees smoke from the engine compartment, …