There is a breather hose that goes from the fuel tank to the evap tank above the spare tire, then a vent hose from that tank goes up to the area around the gas filler which provides the vent to atmosphere to allow air to escape from the fuel tank when filling. There is a paper filter assembly that gets clogged with dirt and it no longer vents, causing the gas filling problem. I made a post about it some time back, maybe 6-12 months.