SUMMARY OF INFORMATION FROM MANUFACTURER:IT APPEARS THAT THE GASOLINE INTHE FUEL TANKS OF THE CHEVROLET P-30 CHASSIS VEHICLES VOLATIZE INCREASINGTHE PRESSURE WITHIN THE FUEL TANKS.THE FUEL RESERVOIR SYSTEM IS CLOSEDREQUIRING THE GASOLINE VAPOR TO BE REMOVED THROUGH THE CARBON CANISTER ATTHE FRONT OF THE VEHICLE.THE CAPACITY OF THE CANISTER TO PROCESS THE GASVAPOR IS LIMITED BY AN ORIFICE IN THE CANISTER INLET LINE (THE ORIFICE ISDESIGNED TO RESTRICT LIQUID GASOLINE FROM ENTERING THE CANISTER).THEFUEL LINES ON THE RAILS PARALLEL TO THE EXHAUST SYSTEM.WHEN PRESSURE DOES BUILD UP WITHIN THE FUEL SYSTEM, THE FUEL CAP DESIGN DOES NOT APPEARTO ALLOW FOR CONTROLLED PRESSURE RELEASE ALLOWING GASOLINE TO SPEW FROMTHE INLET PIPE.ANALYSIS:WHEN THE VEHICLE IS OPERATED IN PARTICULARLY HOT DAYS (AND/ORHIGH ALTITUDES) THE GASOLINE IN THE FUEL TANKS CAN VOLATIZE IN EXCESS OFTHE CARBON CANISTER CAPACITY ALLOWING PRESSURE TO BUILD IN THE FUEL TANKS.IF THE FUEL CAP IS NOT DESIGNED TO ALLOW CONTROLLED PRESSURE RELIEF DURINGREMOVAL, GASOLINE MAY SPURT OUT OF THE INLET PIPE RESULTING IN A POTENTIALFIRE.PROPOSED ACTION:CLOSE THIS PE ON GM AND OPEN AN ENGINEERING ANALYSISINVOLVING VARIOUS MOTORHOME MANUFACTURERS BUILDING ON THE GM P30 CHASSIS.===