[JFP in PA]

The fuel system in the Boxster has no external vents (it is “closed loop”); as such, it is possible for the fuel tank to develop internal pressure or vacuum if the EVAP system is not working correctly, depending upon what the fault is. The car does not like this when it happens, it can run poorly, stall, or refuse to start. The trick is fixing it has always been to make sure the fuel delivery system (pump, etc.) is working correctly, and then find and eliminate the source of the venting problem.

Next time your car won’t start, remove the gas cap, observing if the is pressure or vacuum (either one will “hiss”, so you need to be observant). If the tank is strongly pressurized, it is not venting into the engine through the EVAP control system.