I recently replaced the fuel accumulator on my 1987 420 SEC. One end of the accumulator attaches to a metal fuel pipe with a nut at the end of it. I had a problem fitting the new accumulator, as the nut would not turn, so I turned the accumulator by hand until it was tight. There are no fuel leaks.
However, I am a bit concerned, as I would have thought that you would have to turn the nut with a spanner to secure the fuel pipe to the accumulator, rather than turn the accumulator itself. Can someone confirm whether the nut is fixed to the pipe? If it is not, then the nut must be seized/rusted against the fuel pipe, and I will replace it.

I just replaced accumulator on my 560sel, the nut turned.