I had the same issue on my 2000 HR Endeavor. I was able to access the top of the tank from one of my storage bays. Make sure you look from both sides in the compartments right behind the rear wheels. My passenger side compartment had a narrow panel in the back that once removed (8-10 small screws) provided room to get to the top of the tank. On my unit all of the storage bays are one piece construction made of thick molded plastic that was placed on the chassis before the body was set on. Was able to cut a hole through that material right above the fuel pump/fuel line hookups.
I tried replacing only the short piece of hose above the tank but still had the same fuel problem. I ran a new single hose all the way from the tank, bypassing the metal sections and never had any more issues. Just followed the same route and ty-wrapped the new hose to the old line.
Good luck let us know how it turns out.