My Ryobi electric pressure washer seems to have lost about 30 percent of the pressure it used to spray with. What causes that and how do I fix it ? It is a 2000 psi model and 6 months old.

SOURCE: Ryobi 3000 psi pressure washer detergent injector

Most detergent injectors work by the venturi system. That is that the detergent is drawn into the stream by the forward flow of the water thru a very narrow port after the water passes thru the pump. This system works best when the pressure at the tip of the wand is low. Trying using a very large tip to draw in and apply the detergent, then remove injector and rinse with high pressure. Not good for the pump but to apply soap reliably under high pressure the soap needs to be injected through the intake of the pump. enjoy

SOURCE: I was using the pressure washer and it stopped

This problem, where the unit continually switches on and off when the handgun is closed, is quite common. Unfortunately it has at least six different possible causes, only two of which are easily checked. 
The first thing you can do is look for leaks.  Even the slightest leak will cause this pulsing because the unit gets up to pressure, switches off, loses pressure, switches back on again, comes back up to pressure, switches off... and so on.  This repeated switching is not good for the motor and should not be allowed to continue for longer than necessary to observe what's happening.
So... 1. Does the handgun shut off completely, or does it drip? If it drips, it may simply be because a seal has failed. The handgun can be dismantled, checked, and any defective parts replaced; be sure to lubricate O-rings with silicone grease when reassembling. As a last resort, the whole gun may need to be replaced.
2. Are there any visible leaks at the high-pressure hose screw connections?  If so, most likely an O-ring needs replacing - again lubricate the new one well with silicone grease.
3. If there are no visible leaks, either from the gun or from the connections, all other possible causes are internal within the cylinder head or control head of the pump. New parts will be needed and this normally calls for a professional repair, although it's not beyond the scope of a truly competent amateur.
I hope this helps. Any further questions, just ask! Please remember to rate this response.

SOURCE: oil for a troy bilt 2550 psi pressure washer pump

What fluid and how much is required in the Troy-Bilt 2550 power washer pump?

SOURCE: My Karcher pulses when on standby,stops when i use

Is there a leak from the bottom ?
If so Problem, the leak is from the seam of the Manifold housing. There is a small crack in the seam. A design weakness.. A New Manifold Complete Replacement approx. $61.03.
If not you may replace the Pump Manifold Housing from Karcher, or locate a local Karcher Service Center.
If under 1 year old, and you can find a receipt,Karcher will replace the entire Pressure Washer under warranty.