I wanted to piggyback on this, because Im having a very similar issue. System has been running fine for a few months now, (i bought used from a local guy, he had no issues). A couple weeks ago I noticed no spray on the gauge, after inspecting things I figured out it would not spray past the FAV, even with 12v applied. Jeff from Howerton suggested the FAV maybe contaminated/swollen shut, I tried drying it out for a week, ran distilled water through the system, replaced the FAV, it ran for a second or 2 with 12v applied and cut out. Replaced the entire FAV t, ran perfect with 12v applied, ran it for an hour to dial everything in again with no problems, parked the car overnight and went to drive the next morning and no spray again. I am leaning towards a bad relay/or sticking relay but could use some additional advice. Pics of board back and front attached.
http://imgur.com/gallery/LfOdf