Ryobi RY14122 Pressure Washer - no auto shut off

I have a Ryobi model #: RY14122 electric pressure washer,
Serial #: BM14471D010317.
 
The machine doesn't turn off when I release the wand handle.
 
Several times I've disassembled, cleaned and reassembled the pressure valve that activates the electrical pressure switch; (310870002). The pressure switch tests to be functional.
 
Even though I've attempted to service this valve, the small white plastic plunger that activates the pressure switch doesn't move regardless whether the wand handle is activated or not. I'm inclined to believe this is a common problem.
 
What could be the problem?
Is there a diagram of the pressure valve available?
 
(See attached image file)
 
Steve Cloer
[email protected]