ANALYSIS OF THE MANUFACTURER INFORMATION:IT APPEARS THAT THE PROBLEM OCCURS ON THE WINNEBAGO MOTORHOMES EQUIPPED WITH AN AUXILIARY FUEL TANK AND HIGH UNDERCARRIAGE TEMPERATURES.ANALYSIS:FUEL RESERVOIR OVERPRESSURE RESULTS WHEN THE MOTORHOMES EQUIPPED WITH AUXILIARY FUEL TANKS ARE EXPOSED TO HIGH UNDERCARRIAGE TEMPERATURES WITHOUT A MODIFIED FUEL CAP AND EVAPORATIVE EMISSION CARBON CANISTER.THE EXISTING COMPONENTS MAY NOT REDUCE THE FUEL PRESSURIZATION THAT CAN RAPIDLY BUILDUP FROM THE LARGE SURFACE AREA OF THE PRIMARY FUEL TANK.OPERATING THE VEHICLE FROM THE AUXILIARY FUEL TANK WITH THE PRIMARY TANK FULL COMPOUNDS THE PROBLEM.HIGH UNDERCARRIAGE TEMPERATURES INCREASE THE FUEL VAPORIZATION.STATUS:WINNEBAGO HAS RECALLED THE SUSPECT VEHICLES TO ALLOW VENTING THEOVER PRESSURE (87V-155).CLOSED 1/6/88. #===