Pressure washer help

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gmcman

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I picked up this Karcher HD3500 and I've discovered the pump surges and the pump leaks oil. I've read about the unloader valve but I've been all over this pump and cannot locate it.

I think the oil leak is a worn O-ring as it's flush or slightly recessed in the housing, but the surging is pretty much, full pressure for a couple seconds, then no pressure for a couple seconds, etc. My well water supply is 6 GPM at the end of the hose, the unit is 4 GPM.

Can you tell by the pic where the unloader valve is? Can I run something through it to loosen everything up that may need it? I opened up the pump and everything looks ok, not a huge amount of build up, barely any.
 

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I picked up this Karcher HD3500 and I've discovered the pump surges and the pump leaks oil. I've read about the unloader valve but I've been all over this pump and cannot locate it.

I think the oil leak is a worn O-ring as it's flush or slightly recessed in the housing, but the surging is pretty much, full pressure for a couple seconds, then no pressure for a couple seconds, etc. My well water supply is 6 GPM at the end of the hose, the unit is 4 GPM.

Can you tell by the pic where the unloader valve is? Can I run something through it to loosen everything up that may need it? I opened up the pump and everything looks ok, not a huge amount of build up, barely any.


You may also have a stuck plunger. In the MiTM that I have the unloader valve is located on top of the inlet/outlet assembly.

I've found that winterizing the pumps before an extended layoff helps to lubricate the plungers & makes for easy operation in spring
 
Ok, I did locate the unloader, it's behind the pressure adjustment knob..and yes, on top of the inlet.

How hard should they be to move? I removed it and lubed it up but it takes a little force to move it back and forth, not a terrible amount though. I would guess about 10 lbs of force.
 
Ok, I did locate the unloader, it's behind the pressure adjustment knob..and yes, on top of the inlet.

How hard should they be to move? I removed it and lubed it up but it takes a little force to move it back and forth, not a terrible amount though. I would guess about 10 lbs of force.
Imo it depends on the last time it was moved.

When was the last time you replaced the pump oil?
 
When I picked up the pressure washer, we only ran the engine...only a couple seconds. The GX390 is a beast, reliable engine and it's been well taken care of as far as the engine is concerned. The pump is another matter, and I knew this when purchasing it, but despite not being able to test the pump, if I had to replace it I'm still way ahead of the game and I'm fine with that since I will know it will have a lot of life with a new pump.

That being said, there was maybe an ounce of oil in the pump that came out of the drain plug. I filled it with pump oil and tried it out. That's when I noticed the surging and when I shut it down I noticed the oil leak so that explained why the pump was almost empty.

I've only has this unit for 2 days, but I'm looking at the General AR pump since rebuild kits are ridiculously expensive for this stock pump.

May just need the unloader valve, a few seals and O-rings but what if the pump was run dry for an extended period? That part I'm unsure of.
 
It's pretty easy to screw up the pump. One way is to run the engine for awhile w/o water going through the pump.

I agree, not sure how long it had been run before. We ran the motor for about 3 to 5 seconds. Alot of variables here....with the history being unknown I'm likely just going to replace the pump. Last thing I need is a fatigued pump to self-destruct and possibly bend a rod in the motor.
 
I had one that was surging just like that. I pulled it all apart and lubed the pump valves and cleaned a ton of calcium out and it worked for a bit, and started doing it again. Maybe I did not properly identify the issue...

It ended up being so expensive to find new valves I just bought a newer pressure washer.
 
sound like leak buy on on pressure side i have rebuilt alot of these pumps need a v packing kit check this out like said before it could also be check valves and the unloader valve watch the video so you know how to test the unloader
 

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general pumps are the most expensive to fix but ebay helps me out i got complete v packing kit for 40.00 dealer want 140.00 check and make sure plundger is not cracked
 
Informative video, thanks.

I went ahead and replaced the pump. My unloader was internal and I also had leaks at multiple O-rings. I bought an AR 4000 PSI pump with external unloader and works very good. I will likely sell mine as is for parts or if someone wants to throw $50 to 100 bucks into it.

Thanks for all the tips and help.
 

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