DeVilbis pressure washer pump?

I have a pump that I inherited from my father. It has a 5 hp Honda engine and a DeVilbis pump. He said that it had sucked in the rubber washer and metal screen from the water hose inlet and the pump was damaged as a result. He said it was stuttering and not putting out full pressure after that.

I disassembled the end of the pump and found that one of the three valve retaining castings (unfamiliar territory here, no idea of what it's called, the aluminum side of the pump has three cast in "fingers" that touch the valves on the brass side) was worn down to a nub while the other two were fine. Also, the corresponding brass valve was popped out on the brass side with the unloader.

So since there is no way to order this part and it would probably be prohibitive to do so, I found the same pump on Ebay. Problem with this pump is that it says it came off of a 10 hp engine. The seller claimed that the pump was working but the engine was oil starved.

I installed the new pump, turned on the engine, and the spray works perfectly... except that it isn't particularly strong. My electric Karcher (the smallest they make..1000 or 1500 psi) is far superior in output.

Plus, as I was using it, the oil fill cap started to weep oil that looked like it had metal powder in it.

There is nothing wrong with the engine, aside from the pull breaking and it taking forever to pack the spring back in.


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Is this another pump on its way out? Is this pump maybe valved differently since it came from a 10 hp engine and I have a 5 hp? Should I try and swap the brass side with the valves and unloader from my original pump to the new one? What's up with the oil coming out the top?

 

The oil coming out has a greyish sparkly look? If so, sounds like that pump isn't much good.

 

I have to reexamine the oil, i think it might have had tiny bubbles in it. The original pump had grey oil so that for sure was eating itself.

What could cause the oil to be forced up through the filler?

I think I'm going to swap the valve sides and leave the new piston side of the pump installed. Is there anything in the unloader valve i can clean or adjust? Mine seems to be a brass cylinder with a torx cap on the top.

 

Ok, well I didn't get to look at it until just now and it is late, dark, and starting to rain.

What I did see is this: The pumps are completely identical down to the same pump part number. The unloader valve is also the same part number. EXCEPT that there is a threaded top on both valves with a threaded adjustment plug. The original pump with 5 hp engine had the plug threaded in about 1/4 from the top and the new pump off the 10 hp engine was almost at the top.

Is this some sort of pressure setting? I swapped them between the pumps and will try again tomorrow.

 

I don't know without looking at the pump diagram what your adjustment is controlling, possibly pressure output. The unloader can be taken out and cleaned. Sometimes they need new o-rings and other parts that can be seen once it's apart.

 

http://www.devap.com/repair_pdfs/PW/DAPC/pk18219.pdf

The unloader is #27 in the diagram. If you zoom in on the PDF, you can see on the top there is the adjustment plug I was referring to.

I can say for sure that all the o rings are very hard in the valves, piston seals, unloader, etc.. I suppose I ought to replace all the seals if after testing, the original unloader with the different adjustment increases output.