HEY SORRY TO DO THIS BUT I HAVE A 2000 xj sport 242ci auto and the MIL just turned on with a p0455 code but i does not always turn on......

when it does i can smell gas

i can clear in and it will stay off for a little bit

i also have poor MPG

i leave for a trip in 6hrs need help now plz help

 

Code says it is an EVAP emission control system leak (large). Has to do with the fuel tank, charcoal canister and all of the related hoses and purge valve if any on a Jeep. I am a little more familiar with Ford's system.
A real short explanation since I don't know much is this. The fuel tank builds up pressure from the heat. There are vent hoses running from the tank to a charcoal can up front and probably some purge valves and hoses. When the Engine control computer sees that the time is right, can is full and engine is above idle it purges the can into the intake so it can burn off the fumes.
Sounds like you have an open hose somewhere between the fuel tank, charcoal canister or intake.
clint

 

could be a cracked vacuum line or a cracked evap canister

 

Check around that evap canister. Its on the drivers side before the rear wheel. I had a disconected pvc. Check the two hoses connected to it. That is what causes it. If not, try a new gas cap.

 

try a gas cap or look for a vacuum or evap line that's off or broken

 

check the purge solenoid. also check the rubber connectors on your vacuum lines. also check what the guys above said. i had the same problem. i traced my gas smell to a cracked injector.

 

Thanks every body for the help.. i just went around and made sure everything was connected and tight (including the gas cap) i didnt find anything... cleared the codes .. so far no MIL :-)