The bleed circuit came about as a
result of two Eggenfellner Subaru accidents/incidents traced to fuel
starvation. They hashed it over on the Subaru group and the simplest
solution was to add a bleed circuit between the fuel rail and the return line
(bypassing the pressure regulator), allowing any trapped air to be easily
forced out of the system. Preventing "weeping" of the injectors
was a secondary benefit.
The need for a bleed is dependant on
fuel system design. If you can be sure that there is fuel at the pump
inlet for re-prime, then there is no need for a bleed. IOW, if there is
any point in the line upstream from the pump that is higher than the pump,
there is potential for a bubble of trapped air. Air at the pump inlet may
not allow the pump to force any flow through the pressure regulator.
A good way to avoid injector ‘weeping’
(which would only happen on a faulty injector), or residual pressure in the
rail, is shutoff the pump first in your shutdown sequence.
At least that’s my opinion .
. .
Al