Excell VR2522 Pressure washer - sudden loss in pressure.

You'll need to know who manufactured the motor (Honda, Briggs & Stratton, etc) along with the model and serial number. With that information, you can do an online search for small engine repair manuals and retrieve the specs for you particular motor.
You can even call your local outdoor power equipment repair shop, they'll provide you answers to your questions.

What is your model #
http://www.ppe-pressure-washer-parts.com/excell-devilbiss-pressure-washer-replacement-pump-parts

Anon, The wheel is probably held on by a push nut/cap. The easy way to remove is to cut through the cap retainer with a dremel tool part way and pry off with screw driver, these caps are not normally reusable after removal, check hardware store for replacement.
Check the attached links,instruction and guides, Good luck
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DeVilbiss Excell VR2522 Type 0 Gas Pressure Washer Parts
Remove CM 1200 Lawn Mower Wheel Retainer Clip on Lawn Mower Wagon Carriage...
https://answers.yahoo.com/question/index?qid=20130208122204AAcj7mW

Is the garden hose connected and turned on?If so make sure that the trigger on the gun is being pulled while your trying to start the engine! The backed up pressure in the high pressure hose can mimic a blown or seized engine in this situation.

That pressure washer uses a Honda 5.5 hp overhead cam engine
You need to get the model number of the Honda Engine and then Click Here to go to the ereplacementparts.com website and put the engine model number to order the parts.

I like http://www.ppe-pressure-washer-parts.com/excell-vr2522-replacement-parts-pump See pump upgrade and compare to rebuilding. Another good site is www.pressure-washer-parts.com. Piston seals usual begin by overheating from excessive idling. You might add a thermostatic relief valve to help this.

check oil filter/sump gasket or sump oil drain plug copper washer

Did you check the hose that goes into the resevoir.
Vitally

should be a honda gcv 160 5,5 horsepower engine.

do a search for honda engine carburretor adjustment, plenty of pages on the internet detailing how to adjust carbs, mixture etc.

Excell Pressure Washer Model VR2522 Replacement Parts repair kits ...
lok at this site , parts breakdown of engine etc

Sounds like the diaphragm in the pump unit has failed, the engine and the pump are two seperate things the engine only operates the pump but if the diaphragm is leaking or broken you wont get any pressure