RTH Big Bend Black Gap Road. Looking for speedy help/diagnosis. Here are the elements. 30 mile rough washboard difficult road wheeling for 4 hours full gas tank 115 degrees outside finished difficult trails while on the highway sudden strong gas smell coming from AC vents. Stopped on the side of the highway hissing sound coming from driver side fender canister, opened gas cap slowly and pressurized air with some small drops of fuel expelled under pretty high pressure, continued for at least one minute. No leaks around injector rings, rail, filter, zero sign of fuel or fuel leak anywhere just hissing sound on cannister. After pressure calm down drove another 20 mins and pressure came back. It appears as though high prssure is building up and not going anywhere not sure if it the heat and the washboards or malfuncion. Thanks for the help.