[El Dorado Jim]

Like Jason said, I would use a hacksaw to cut the rim of the cap off and then I think you can see the tabs that hold the cap on, maybe you can then use a screwdriver to push the spring loaded tabs in and remove the cap,or you may be able to hacksaw the whole cap off at the top of the filler neck , you may have to flush your tank after that,but better than destroying your tank with a pipe wrench or channel locks...