Had this on 2010 Escape. SOLVED! My rear wiper motor was fused, draining my battery. I pulled the fuse. Washer fluid pump still working… A week later I removed the bad rear wiper motor ( on the glass of the hatch), getting ready to replace it the next day. After I unplugged the power to the rear motor, MY WIPER FLUID PUMP WOULD NOT WORK. Today I just now put a new motor back in and WIPER FLUID PUMP WORKS AGAIN.
My conclusion. Nothing wrong with pump, but ground for circut must go through the back motor, ( still worked with rear wiper motor fuse out).
Sounds crazy, but true!