300CE fuel tank problems
 

Hi All,

A few months ago my fuel gauge started misreading, I assumed the fuel sender unit was wrong. I tried to remove it but it wouldnt come out. I rattled and shook it and replaced it and it worked fine for a few weeks. Recently it failed and I tried to remove it again last night. Boy!!! I ended up having to break it up as it wouldnt come out, and when it was out a bit, wouldnt go back in to its proper seating position. When I had the top bit out, the tube bit fell to the tank bottom (nice rolling sound) and then I saw that from the tank roof, a sort of plastic sealing layer had fallen/collapsed and it was this that had prevented the sender unit from getting into its rightful place. The sealing layer took a lot of pressure to move, it was quite rigid.

Has anyone ever come across this before?? When I bought the car the previous owner had mentioned about a new fuel tank being fitted. I'm wondering was it a non original tank??

Any thoughts?? Thanks Gerard

My $0.02...
 

I replaced the sender in my 300E not too long ago. Also replaced the unit on my 280E. The entire sender unit came out easily as one piece. I don't think there shouldn't be any resistance at all when removing the unit. If fits in/out perfectly.

Update!!
 

I figured what was wrong with my fuel tank. At the weekend I took the tank out of the car to remove the aluminium tube bit of the fuel sender. It was rolling around too much in there!
It was then my dad and I reckoned the fuel tank had been dinged or bent, maybe by a heavy load in the boot (trunk, heh heh) hitting against it. We gently pulled it out using a short bit of wood and a rope inserted in the fuel sender hole. After a little bit of pressure, the tank 'popped' out, and now the fuel sender hole is at a little angle off the vertical, where previously it was vertical.

It was this angle that stopped me from taking the fuel sender unit out. Now I have to get a new sender unit!!

gerard

PS, I thought originally that a sealing layer was coming away and pressing on the sender unit. It was fine, it was the fact that the hole was pushed back, and the sender was then pushed back against it. I dont think it is a seal either, it looks more like piping or channels, Mercedes puts a lot of plastic bits inside the tank!!

Question,
 

I am also looking for a special tool. I have a '88 300SE and I would like to clean or replace my fuel gauge sending unit. I want to say off the top of my head that the size of the socket need is 27mm. or a 1 13/32 I think.. Not sure, any suggestions?

I'm not sure about the SE, but on my 124 CE its a 46mm socket. I bought a nice Snap On for the job!! Saves monkeying with adjustables and sliders.
gerard