Fuel evacuated capsule in the aircraft fuel system?

Question

HI, why is this capuse situated here and the purpose please.. i cudnt find ne thing helpful so far

Answer 1

Its the float valve in the carburator or if i remember it right (20 yrs. ago am a component mechanic) this evacuated capsule as plane goes higher and density decreases this capsule collapses restricting the flow of fuel to get a good mixture cause air has thinned.

Answer 2

I'm not entirely sure what you mean with this one but I'd say that Deepseteyes has it partially correct . There is an evacuated capsule made of beryllium copper which leans the fuel/air mixture automatically as altitude increases.