Confusing Unloader Problem

Patrick Harding

Patrick Harding

Member
Hello, I have an unloader on a 3,000 psi 8.5 gpm machine that I can't seem to set correctly. I am only able to set the flow pressure to about 1,800psi before my spike pressure starts hitting 4,000 psi. We have a second machine that has the exact same setup, going through a heater and 200' of hose, and that one I can get to 2,500 psi flow pressure and a spike pressure of 3,500 psi, which seems acceptable. I have pulled the unloader apart trying to see if there was a damaged seal, sticky piston, etc. Everything looked good except for the end of the piston, part that's hitting the ball bearing, was beat up so I switched it out with another one I had lying around but it didn't help. I pulled the unloader line out of the water tank to see how much water was flowing while I had the trigger gun on. I had quite a bit coming out making me think the problem lies with the unloader and not the pump, could be wrong about that though. If anyone has some insight into what's happening I would appreciate it. Thanks in advance for your help!

(I'm using a green spring unloader 21gpm 4,050 psi. Also I have my pressure gauge at the end of my hose right before my gun. It case this helps I'm also using a #9 tip, which is an 8gpm tip I believe. I think its a size too small but it was the closest I had)
 
Patrick Harding said:
Hello, I have an unloader on a 3,000 psi 8.5 gpm machine that I can't seem to set correctly. I am only able to set the flow pressure to about 1,800psi before my spike pressure starts hitting 4,000 psi. We have a second machine that has the exact same setup, going through a heater and 200' of hose, and that one I can get to 2,500 psi flow pressure and a spike pressure of 3,500 psi, which seems acceptable. I have pulled the unloader apart trying to see if there was a damaged seal, sticky piston, etc. Everything looked good except for the end of the piston, part that's hitting the ball bearing, was beat up so I switched it out with another one I had lying around but it didn't help. I pulled the unloader line out of the water tank to see how much water was flowing while I had the trigger gun on. I had quite a bit coming out making me think the problem lies with the unloader and not the pump, could be wrong about that though. If anyone has some insight into what's happening I would appreciate it. Thanks in advance for your help!

(I'm using a green spring unloader 21gpm 4,050 psi. Also I have my pressure gauge at the end of my hose right before my gun. It case this helps I'm also using a #9 tip, which is an 8gpm tip I believe. I think its a size too small but it was the closest I had)
Click to expand...
If the tip is too small, you are going to bypass water. I'm pretty sure you should have the gauge on the pump or right after the pump to set the unloader. It sounds like a bad unloader if the spike is at 4000, and you a only at 1800, unless you are way off where the unloader should be set. And a 1000 psi spike on a 3000 psi machine isn't right either. It should be 300, from everything I have read and experienced. But if you are reading the gauge at the end of the hose at the gun you are probably a lot closer to ok.

Your nozzle should be a #10 for your pump specs. There is a big problem right there. With a #8 tip on that machine you are bypassing 2 gallons.
A #8 tip at for a 3000 psi machine comes to 6.5 gpm.

http://www.pressureparts.com/nozzlecalculator.aspx/
 
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Ralph Q said:
If the tip is too small, you are going to bypass water. I'm pretty sure you should have the gauge on the pump or right after the pump to set the unloader. It sounds like a bad unloader if the spike is at 4000, and you a only at 1800, unless you are way off where the unloader should be set. And a 1000 psi spike on a 3000 psi machine isn't right either. It should be 300, from everything I have read and experienced. But if you are reading the gauge at the end of the hose at the gun you are probably a lot closer to ok.

Your nozzle should be a #10 for your pump specs. There is a big problem right there. With a #8 tip on that machine you are bypassing 2 gallons.
A #8 tip at for a 3000 psi machine comes to 6.5 gpm.

http://www.pressureparts.com/nozzlecalculator.aspx/
Click to expand...

Ok, Thanks for the info. That's helpful knowing where to put the gauge. I guess there would be a lot more spike pressure after the unloader due to all the hose.

You said I might have the unloader way off. I just want to make sure I'm doing this correctly. when I set the unloader I start with no tension in the spring and gradually adjust to the correct pressure. Is this correct?
 
Patrick Harding said:
Ok, Thanks for the info. That's helpful knowing where to put the gauge. I guess there would be a lot more spike pressure after the unloader due to all the hose.

You said I might have the unloader way off. I just want to make sure I'm doing this correctly. when I set the unloader I start with no tension in the spring and gradually adjust to the correct pressure. Is this correct?
Click to expand...
Yes. With the gauge right at the pump, just slowly turn until you get to 3000 psi, then the spike should be 3300 + or -. But the first thing they say when setting the unloader is to use the proper sized tip. You are spinning your wheels until you get a #10 tip according to nozzle calculator. You should PM Russ Johnson. He walked me through my setup and it went off without a hitch. He can tell you if it's possible to set an unloader with the wrong size tip.
And there is thread on here somewhere that states the spike is higher at the end of the hose. So that could be a problem too.

Another way to set the unloader is to watch the bypass and when there is a drip coming out it is set. But you need the correct tip for that. My unloader bypasses zero with the right tip or bigger with a wand or surface cleaner.
 
Ralph Q thanks for the replies! I don't know if its just me but the newer green spring unloaders don't seem to last. Between these two machines they've only held out for a year each. Anyways, I now have some things to try out. Thanks!

-Pat
 
Green spring only seem to last 150 hours before they would cycle into bypass every few seconds. Had it happen on 2 different machines with completely different setups.

I have been running that unloader Russ mentioned above for 200 hours not an issue. Have a second on order to replace another green spring problem in my other setup.
 
That's good to know. I'll be trying that one out. I looked at the old unloaders lying around and found that this is actually the 3rd one to go this year. Lame. I wouldn't mind paying a little extra for something that will last because it saves money in the long run. I hate it when manufacturers sacrifice quality.
 
I have the Giant Orange "Spring" unloader,..This unloader uses compression washers as opposed to a spring.
An unloader block is necessary in my opinion with this unloader,... Too heavy to be hanging from the side of a pump head.

Jeff
 
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