[RUSTY 38]

I too have the dreaded Dewalt 3100 with a bad unloader. My problem isn't the fact that it won't develop pressure but I can't start it unless the trigger is pulled while starting the washer. When I release the trigger, the motor dies. The valve looks pretty good, but the o rings look like they could be replaced.
What I was wondering is how tight to tighten the spring with the brass cap with the Torx hole. Do I bottom it out or back it off some? Is there maybe a torque spec? Anyone have any ideas?

 

[RUSTY 38]

So the unloader valve on that was preset to 3100 psi. The brass cap that compresses the spring will also adjust this pressure. The more it is turned out the less nozzle pressure at your gun. The more the spring is compressed the higher the pressure at the nozzle. So if you bottom that cap out you are not allowing the unit to go into "bypass mode" when you release your gun. Ebay sells a nice pressure gauge that goes in the pump outlet and you connect the hose to that to see your hose pressure. If you tampered with that knob you adjusted the pressure and the engine is stalling because of the pressure spike at the pump.

I copied this from a site:
Using the Unloader to Regulate Pressure

In the specific case of the pressure-actuated unloader, pressure can be controlled to a certain extent by adjusting the tension on the spring holding the piston in the valve in place. (Remember, this is called a pressure regulating unloader).

An unloader is not an absolute, on-or-off device. Rather, it can allow a certain amount of flow to bypass the hose to the gun and return to the inlet side of the pump. The amount of by pass is et by tightening or loosening spring tension with a nut or hand grip on the end of the unloader opposite the outlet port.

This means that the flow of water to the nozzle, and consequently, the amount of pressure produced at the nozzle, can be regulated to some extent by adjusting a pressure-actuated unloader.

Thanks Old Man, that is exactly what I thought, I just wanted confirmation.