Engine lite on 2002 4.0 new gas cap - Jeep 2002 Grand Cherokee LAREDO

V A new gas cap dose not always solve the problem with the EVAP system .
And understand the concept of the system is unsound to begin with .
What its supposed to do it store fuel vapor in a sealed system in a charcoal filled canister at the rear near the fuel tank .It has a vent valve from the tank to the canister most likely problem .The vent valve has a filter air needs to get in so the tank can vent into the canister but vapor can't get out .Its an electrically controlled solenoid that opens in conjunction with the canister purge solenoid located on the intake manifold .
When the engine rpms reach a high enough speed the purge valve is supposed to open and burn the fuel.
With cheap materials from China the fuel system rusts out the tank the lines all of the seals in a few years add road salt you are left with nothing except a government mandate drafted by fools .
The last time I filled up my tank hundreds of times more fuel vapor went in to the upper atmosphere then my vehicle with the evap not working in a year .