280c Fuel sending Unit
 

I have recentley purchased a fuel sending unit for my 1974 280c. The old one was erratic, innacurate, and sometimes the low fuel light would not come on. The replacement part arrived today, and on the side of the unit it says Attention: remove safety pin before installation. There seems to be only one thing they can be talking about. At the bottom of the unit which is cylindrical in shape in the center is a small spanner style nut. This nut is also incased in a plastic sleeve. It has a blob of green paint on it. Is this the afore mentioned pin, and if so, how does one remove it with oout damage.
Also, how hard is it to replace the tank fuel screen? looks like a bear to me on a car this old.

The pin they are talking about may already be removed. It is used to keep the float from banging around in transportation. It goes through a small hole in the lower portion of the outer wall (not from the bottow but through the side).

Try slowly turning the sender end for end. If the float can be heard moving then the pin is already gone look for the small hole probably about 1.5mm dia.

BTW, the design of MB sending units has stabilized their readings by only allowing fuel to enter through that small hole. When removing the old unit one will notice that the fuel flows from this hole for some time. When cornering or traveling in hills that change the attitude of the tank, the readings stay stable as the fuel takes times to change levels inside the tube. It is this vent hole that the pin would be in, if it were there. If you aren't sure remove your old sender and watch where the fuel comes from it.

Fuel sending Unit
 

Thanks Steve
I located the pin, it was under the yellow warning tape that instructs one to "remove transport pin", therefore I would have never known it was under there until your response. Have you ever replaced the fuel screen in the bottom of the tank? I have the part and would like to know what pitfalls are in store for me when I replace it as well.

Thanks again