2005 Porsche Cayenne when filling the fuel ,the car start i

we found the problem is the carbon tank valve,and i think this problem happened when the fuel tank is empty.the fuel tank is full of gas air,we filling the gasline to the tank ,all the gas air get into the Carbon tank .if the Carbon tank valve cannot hold these gas air,let them into the intake manifolds .the Mixture will get heavy while we starting the car .
so the car could not get up in the first and second time.

You are correct. The purge valve is located next to the intake manifold.When it sticks open it allows fuel vapor into the engine and it floods the intake with fuel vapors creating a hard start condition.Sometimes it will create a check engine light on.