If it were mine, I would consider draining out the rest of the fuel,and try putting a heating pad(s) around it . Let it get warm.Then I would set the air compressor regulator at a low pressure and carefully try adding air to the tank like Art suggested. Not sure what kind of cap you have but would rig up a way to get the air in there through the fuel line or something-taking care not to bust the tank.. bordercollie