2005 Malibu Wakesetter VLX Front and Middle Tank won't fill

[Kitch]

Okay, I'm at my wits end.  My front and middle tanks won't fill reliably.  I've pulled all 4 piranha pumps and all are clean and working - 12V, breakers work, switches work, ball valves clear.  What am missing?  Rear tanks fill/drain every time, middle tank fills sporadically, front tank just won't fill?  Suggestions? 

[gahvey]

Anything plugging the lines?  If it is on the trailer, try using a hose (or come up with a bucket and hose assembly) to the pump and verify that the pump is actually pulling water.  You could also reverse the pumps (use the drain as the fill and vice versa) to verify that you can fill and drain.