I just purchased a Simpson Megashot V3000 Pressure Washer and noticed the engine would stop running every time I released the wand trigger. Also, water was constantly spraying out of a valve underneath the unit - I assume it's some type of pressure release valve but there is no mention of it in the owners manual. I am thinking about returning it to Costco for a refund.

SOURCE: I have a dewalt 3750

I worked at a tool rental center while attending college and learned many tips and tricks about Dewalt and other brand pressure sprayers. Your machine probably has a 13 hp honda and has max pressure of about 3500 to 3700 psi. Most of the problems that customers had were engine related due to severe working conditions including totally wet engine /plug, wet air filter, and or other problems that were easy to remedy. We would set the pressure regulator to minimum pressure and explained to the customer how to increase the pressure as necessary but only after the engine was completely warmed-up to running temp to prevent engine stall. Your machine has a throttle lever between the tank and carb that should be set to max if you are going to set pressure at or neer max range. Most cleaning jobs do not need much pressure. Use lowest pressure to get the job done. Your engine developes around 13hp at about 3600rpm. If you want to maximize the life of you sprayer, then use your machine at about 70% of capacity or about 2000 to 2500 range that will allow you to run your engine slower increasing lifespan. Your sprayer is likely rated at 4 gallons per minute so make sure that the tip is that capacity. The tip has the size stamped which would show the fan degree and flow in gpm. The wrong tip, say a 3.5 gpm will strain the engine to point of stop because the smaller tip increases pressure. Most engine stall is due to high pressure setting on new machines. Lower pressure when warming-up machine and use max pressure rarely when necessary to max life. Please email for other information/questions or simple tests to determine faulty parts, good luck.

SOURCE: karcher k2.40r pulsates

It sems you have a blockage in the tip. If you get a grain of sand in the nozzle it will act like this. Get a piece of fine wire and poke down the nozzle to free it up.

Testimonial: "Thanks, it's fixed. The wire didn't actually clean it out, but I used my air compressor and blew into the tip. Wonderful!!"

SOURCE: pressure washer stalls out when wand nozzle is released

common for not starting unless trigger engaged as you are turning the pump as well as engine creating pressure,as for stalling pump has unloader valve which is probably in need of grease(use good silicone grease)this allows water to ciculate when trigger released.

SOURCE: Engine dies when wand trigger is released

Re-kit the unloader.

SOURCE: Lack of pressure after releasing the trigger on the wand

Hello awcockerill:
This sounds like the bypass (unloader) valve is sticking. Here is a diagram of your machine's pump. On page 2.4 see part #1. The top of this assembly is a black plastic cover. Remove all of assembly # 1 carefully. Under that is part #8. This is the bypass valve. You need to pull this out, check that the o-rings are not bent, worn or damaged, then lube it good with a VERY VERY good waterproof grease. Re-assemble it and all should be well. The part numbers are on the diagram but where to get them depends on were you live. Karcher web site may give you a number to call. Good luck.