Having problem with Quincy 325 Air Compressor Unloade Valve......

I picked up a nice used Quincy 325 air compressor with a 5hp motor, and 80gal horizontal tank. It seems to run great, but when it reaches pressure and shuts off....it's not unloading out of the unloader tower like it's supposed to.

I disconnect the exit site of the hydraulic unloader valve mounted on the side of the compressor crankcase, and when there is air pressure in the tank....and the compressor is turned off with no oil pressure....no air is flowing out of the valve. I'm pretty sure that air should be flowing through it to the unloader tower when there is no oil pressure......and then when you turn the compressor on and the oil pressure builds, the valve closes....and the unloader tower closes....and the compressor starts to build pressure.

Is it possible that something inside the hydrualic unloader valve is stuck? Is this common? According to the manual I found online, there are some check balls in there...maybe they are rusted up?

What should I check next? Any ideas would be great!!

Thanks!

Does the unloader work in continuous mode?

Pull the top of the unloader - they are simple... Check the diaphragm, clean and lube the rest. Look at your control valve - you might have o-rings worn or swollen.

Lakeside53 said:

Pull the top of the unloader - they are simple... Check the diaphragm, clean and lube the rest. Look at your control valve - you might have o-rings worn or swollen.

Click to expand...

The tower and everything inside is in good working shape.....I can bypass the control valve and put compressed air right to the tower, and it will unload the pressure in the head.....so that part is working. I'm just not getting any air pressure through the valve. I pulled the valve out, and everything looks to be ok.....but I need to pull it all the way apart and make sure the balls and spring inside are not gunked up. It's definitely a problem with the hydraulic control valve.

Quincy is still in business. Find their authorized repair/parts location near you and call and talk to the service manager. Those guys know *everything*. Be sure you know your record of change number when you call.

metalmagpie

Well, I found out what was going on. There is a small little brass screen, and some type of fiber filter pressed into the in and out port on the hydraulic unloader valve that mounts to the side of the compressor. The little fiber filters were so gummed up, hard, and full of junk....that they were not letting any air into, or out of the valve. After I cleaned the screens...and tossed the fiber filters.......the valve started working like it's supposed to.

It was an east fix!

FWIW - I had the same problem - brass filter/screen was not letting air pass, so the my compressor would not restart under load. It was not necessary to remove the hydraulic unloader valve, just the nipple on the intake side of the valve.

Thanks for documenting this.

Don