Why won't my sprayer stop? It doesn't seem to need to be pumped

seems as the PSI based switch maybe having issues inside the pump most likely

No make or model, so no help until that is known.

The rear wiper has its own pump motor. pull the hose from the wiper and have someone engage to see if there is a clog. do the same at the motor. if bo liquid comes out then its the pump. also check fluid level in reservoir as well as a possible secondary reservoir

Make sure pump is submerged i water
Remove tubing from pump discharge and see if pump is pumping water/ If so your tubing is clogged between pump and saw. Remove tubing and rinse out with hose.

If an airless paint sprayer won't prime it's usually because one or both check balls are stuck. First try hitting the head where the pump is sharply with a hammer, hard enough to knock the balls loose but not so much that you do any damage to the pump. If that doesn't free them up you may have to take the pump apart and clean them and their seats.
If an airless paint sprayer won't develop pressure, it's usually because the packing rnigs are damaged or collapsed. The only way to check this is to totally disassemble the pump and check them. Also look for any damage to the piston and cylinder. They must be very smooth and shiney, if they are scored they will eat up any new packing rings you put in.

chabunga offered really good info...except for the suggestion to use Vaseline on the 'O' ring. NEVER use Vaseline on anything rubber, because it is a petroleum based product and it will cause the ring to deteriorate. Use a non-petroleum based lubricant instead.

All airless sprayers are on-demand pumps. The two settings are prime and spray. When it is set to prime, the pump will draw liquid from the bucket below and pump it out the side tube and will never stop until you switch it back to spray. When set to spray, the pump will run until the pre-set pressure is reached, then stop. As soon as you start spraying, the pump will run until a few seconds after you stop spraying. Tip size and pressure setting will affect how long after you stop spraying the pump will run. A large tip and high pressure will cause the pump to run longer after you stop spraying.

The filter needs to be cleaned. the cartridge should be removed from the housing and sprayed on the o with a hose and sprayer. A strong, concentrated jet of water works best. I hope this helps.

Hi there
There are many possible reasons for your sprayer not pressurizing. If the pump lever is moving freely and does not seem to be building pressure while pumping it is possible that the O-ring at the valve is damaged, the seal in the pressure regulator is leaking, the piston or the collar is worn. Any of these problems will require disassembly of the unit and inspection of each part. If you do feel resistance building as you pump but quickly loose pressure you likely have leaks in the diaphram, it's seal, the pressure cylinder or the tank itself.
If you are comfortable disassembling the unit and inspecting the parts for wear or damage most of the individual replacement parts are fairly easy to replace and readily available online from Solo or at many retail outlets and supply companies. Solo has done a great job with how-to videos and instructions for each procedure on their web site www.solousa.com
If you are not comfortable disassembling and repairing your sprayer yourself you can try contacting a mower/equipment repair shop in the Redding area as is seems the nearest Authorized Solo sprayer repair center is Cloverdale Saw in Cloverdale CA, 707-894-2273

IT'S AN INTRINSIC FAULT WITH THIS PIECE OF JUNK. THE DIAPHRAM INSIDE THE PUMP TUBE IS ABSOLUTE GARBAGE, THEY DON'T EVEN WORK PROPERLY WHEN BRAND NEW, BUT AFTER A FEW MONTHS THEY WON'T PRESSURISE AT ALL. BUY A QUALITY SPRAYER, THAT REPLACEMENT PARTS ARE AVAILABLE FOR.