At the bottom of the fuel sending unit on a W126 there is a plastic ring around a slotted nut that holds the tube together. Here is a home made tool to get the nut off without stripping the fine threads off of the threaded rod that is in the middle of the nut. I used a dremel to cut a slot into a 1/8 screwdriver. The tip was already broken off of it anyway.

Attached Thumbnails