How do i find a dewalt dp3100 unloader valve - Dewalt DPD3100 Gas Pressure Washer

Check the pressure switch. The unloader valve is actually in the pressure switch where the small air line from the tank check valve attaches to it. When the pressure switch turns the motor off it then lets the head pressure bleed off so the motor can restart the next time pressure drops in the tank. If it's not working and bleeding off the head pressure the cold start valve (the one with the pin in it) also won't open so the motor can restart and warn up properly.

I believe that you have a very simple problem related to the in-tank check valve. Follow the discharge hose from the compressor to the tank. It should connect to a brass or chrome valve. This valve has a one way check valve that allows air into tank and not return to compressor (if air leaks back, compressor will be under load (motor will not overcome) and air will leak from the pressure switch unloader valve). With air in the tank, remove the hose at the check valve and spray soapy water to verify leak, replace part or clean as needed. Good luck

See this diagram:
http://www.mastertoolrepair.com/images/DPD3100_pump.jpg?osCsid=1f3m03ijp5lcht6569kran6rk2

Remove Items 122 (Un;loader) and 138 (Thermail relief). Clean them up as best you can with a nylon brush under some slow running water. Dis-assemble the unloader valve completly to clean (both ends). Then lubrcate them with White Grease and reinstall both parts AFTER placing White grease in the cavity the valves mount into. Very briefly... Test water flow with the engine not running Then start the unit with water off and let run 30 seconds. Turn off engine. Turn ON water supply and test water flow engine OFF. Note you will get a certain amount of white grease initially that passes through the unit. Start unit and rapidly actuate the trigger 1/2 second on 1/2 second off multiple times to force the unloader valve to cycle.

You can get parts here if either of the valves have completly failed:
http://www.mastertoolrepair.com/dewalt-dpd3100-n001194-pump-p-59405.html

The above steps should get your presure washer working properly again.
Thanks for choosing FixYa,
Kelly

The pressure unloader us usually the first part/s that fail. An unloader can fail resulting in no or very low pressure or good pressure, however will not unload when trigger is released and stall the motor. Look at breakdown for your pump and determine if unloader parts are available and reasonable. If too costly to replace these parts then install an ez start valve to help start engine and tie back wand handle to deal with unloader problem (workaround). Ez start valve can be seen here:
http://www.cmcpwe.com/accessorystartvalve.html

When not in use, store washer with oil in pump to displace the water. The oil will help lube internal parts and possibly cause the unloader to begin working (if stuck due to debris/rust). You can find a gizmo to help you feed oil into pump on ebay /other web locations. Good luck with your repair.

If the unloader valve doesn't release the pressure from the compressor it will be hard to start. This is because there will will be pressure inside the compresser. When the tank is full and the compressor shuts off, you should hear a rush of air which is the unloader valve releasing pressure. The unloader is like a one way valve.

Go to http://servicenet.dewalt.com/Products/Detail/DP3100#. On the right side there's a Downloads section, pull the scroll button all the way down, the last download listed is your manual. You can either download a PDF or have it emailed to you.

Unloader leaking, intake clogged, intake valve shot, piston rings worn, or small air leak in the system.

Sounds to me like the check valve is sticking. Where the pipe enters the tank, there is a check valve to keep this from happening. If that valve leaks, it will leak the tank down through the unloader.

How's this

Check the unloading valve. Accumulation of dirt might be preventing the valve to fully close, by-passing a portion of the compressed air.