As an NES, but not a teacher, my understanding would be that it refers to the filter, not the dome.
If I had meant the dome I would have said something like:
"Petrol enters at I and, passing, through[\via] the circular filter gauze F, to the dome D which surrounds the central turret, enters the pump chamber through the inlet valve V1".
I admit it's a bit of a mouthful!
Hope this helps
PS I'd probably also have used the word "that" rather than "which".
- For Teachers