What does not show in the drawing are check valves on each vent on the sump. That allows air to leave the sump but not enter via the vent line.
>If the fuel filter starts to
plug, the resulting low pressure on the suction side of the pump will likely result
in vapor lock especially if the pump is in the engine compartment where it is
hot.
The filter before the pump is actually a gascolator. It has a very large area and is easy to service and drain. The pump is prior to passing fuel through the firewall per Velocity design.
> Filters are best after the pump so they are under pressure and not
vacuum.