Power washer blues

[drf256]

Thanks for all the responses guys. I didn't get any alerts about this.

I took all 6 valves out and cleaned them, no pressure.

I tried it with no tip, no pressure.

I forgot to mention that this happened once in the past and messing around with the unloading valve made the problem go away. I'm gonna have to source one and will report back.

My only complaint on the machine has been its size and weight. It's too much for one guy to handle in terms of lifting.

 

[drf256]

Only 3 possible problems. The unloader (pressure adjustment valve) is bad or has dirt in it, the check valves (little spring thingies under large brass caps) are worn, sticking or have dirt in them, or the packing is worn. Pull all the check valves and make sure they are not sticking. Give them a shot of air to get rid of scale rust around the sealing point. Sometimes they will stick after sitting for a while.

The unloader. Yes it's adjustable, but once set correctly, don't touch it. You can literally explode stuff with it cranked all the way down like that. The unloader is the "on/off". Pump builds pressure (to a set adjustment) then begins to bypass the water back through the pump. If left in bypass for a long period, the water can get hot enough to damage the pump packing. When you key the gun, this allows a new path for "relief" and the unloader valve sends the water through the hose until you close the valve (gun) sending it back into bypass mode. I never had much success repairing the unloaders. A new one should be about $100 for a good one. Flow sensitive is best.

I would hang onto that machine...it's a good one in a world of junk. A replacement that will equal it's performance will be easily over $1000.

Inspect and clean the check valves. (Use needle nose to grab the little nub on top. Wiggle as you pull.) Back that unloader way down (loosen) and try again. If that doesn't work, buy a replacement unloader. There is a special tool required to pull the packing a lot of times. Every now & again it will come out with fingers though. Leathery looking rings sandwiched between plastic and brass. Check all orings for wear. If packing is worn, replace. Should cost around $75. Packing is accessed by removing the 6 or 8 bolts holding the brass head on and pulling it off the three pistons. These pistons are porcelain and can crack if water is left to freeze in the head or they get too hot.

Happen to have a PN and/or Diagram of that unloader valve?

 

[RCBS]

Not 100% sure this is it, but that looks to be an "orange spring" Giant brand unloader. There are literally dozens made by them...this is my best guess..
http://www.giantpumps.com/accessories/22913a

http://www.giantpumps.com/accessories/22913a

The model number might be located on it somewhere....should be able to use Giant's site to look up diagram if that's not the right one. #5, #15 & #11 could be worn and not letting the pump build pressure.

If you get a new one or rebuild that one, when you go to "set" it, use the guage on your machine (hopefully it's accurate) and pay attention to what pressure it unloads at (when you let off trigger) rather than what "running" pressure is. Set the unloader to whatever pressure your machine is rated for (probably 3k or so). If the unload pressure is set at factory spec and your "running" pressure is lower than spec you could have worn packings or washout in the pump head. Tightening the unloader to achieve more pressure will make the unload pressure high and can cause damage.

How did the valves and seats look? Any significant wear on the little steel plate? They can wear and let water by. They are usually nickle plated and should feel smooth. Also, the orings under the valves OK? How's the oil in the pump crank case? If it's milky, you have a cracked piston letting water through. Those are usually cracked either from freezing, or running the pump in bypass too long and getting hot. When you key the trigger again, they get hit with fresh cool water and can crack.