The fuel pump housing is leaking from a small whole within the fuel pump cover. This whole is also shown in picture 4.6C "Showing the fuel pump sealing ring" in chapter 3.4 of the Haynes manual (#0813).
It's the whole on the left side of the arrow.
Surely, it looks that I have to replace the fuel pump after 22 years.
I was only wondering if someone knows what the whole is for and why it is leaking, now. (I haven't opened the fuel pump, so far.)