Think it through. If you have 80 PSI at one end of a pipe (oil gallery in this example) and lets say 70 PSI at the other end of the pipe then you can understand that somewhere in that length of pipe there will be pressure but no flow. And the point of no flow can move back and forth in the pipe as the different leaks off of the pipe come and go.
The way I understand hydraulics is if you have pressure even if it is supplied to each end of the pipe as long as there is an area of lesser pressure in the system there will be flow to that area of lesser pressure.
