Thanks for the quick response!
Ah, I failed to mention that it's an european car. Sorry about that. I fed the serial no. to the
www.realoem.com page and this is the output:
P E30 Cab 318i M40 ECE 19930100 L M
So I'm pretty sure that it is an E30.
The diagram on the lid is only a lot of numbers referring to the fuse/relay location inside the box. And none of the relays present are related to the fuel pump. So my best guess is that it's outside of the box.
I better crawl the net some more while i re-read my Haynes manual then. See if i can figure out the wiring diagrams.
The search continues
Well, thank you for helping me out so far.