to pump
to injectors....
unused fuel is directed back to the tank via the leak-off pipes
cooling matrix
Isn't there a pre filter in the tank?
It is possible you've hit something that knocked the tank, something has jarred loose and is caught up in the feed to the engine (pump), making it suck hard enough to cause the bulb to collapse under vacuum.
Or something got into the tank. I hope it's not the dreaded fungus.
I think it's a possibility something is restricting the flow to the pump and the hiss of air is the rank breathing in.
Years ago, I was called out to look at a 406 petrol injection with a similar issue. The car had been driven over tall grass, which pushed the tanks flat bottom. The suction caused the bottom to be pulled into the pump baffles and it stayed there. Same issue. I lifted the seat, undid the screw ring, lifted out the pump and pushed it back out with a broom handle. The broom allowed the vroom vroom to vroom once more
