Often times if the pressure washer has been sitting for a while, the ball and spring in the unloader can freeze up. This happened on an old second hand unit i had. Disassembling and freeing it up takes about 10 minutes if you're handy.
This was the initial symptom, then it freed up and worked for a while, and while it freed up the crusties, there was a lot of surging in pressure.
One thing the manual (and various internet TSR guides) says that I dismissed was to
check the suction screen for clogs. Me being incredulous, I dismissed this after recalling that I have never seen a screen clog from municipal water. What do you know? I checked, and it was about 50% clogged. It ran fine (relatively except for the unloader sticking) in the morning as water pressure is typically higher until use over the day lowers my line pressure. Then in the afternoon, that seemed to be enough to cause the later in the day issue I was experiencing (low/no pressure).
I cleaned out the screen, purged the lines of air, and it ran fine to finish up the job (steady pressure, too) for about 20 minutes.
This guy was helpful as he reinforced to check lines for obstructions.
Thanks for all the replies.
