Quincy 325 Air Compressor Unloader Valve not working.....

The way it's supposed to work is that when you first turn on the air compressor there is a valve on the high pressure side of the compressor that is held open to unload the pressure until the oil pressure builds to a certain level, then the valve is closed, and the compressor starts building pressure.

For some reason, my compressor is acting like the valve is stuck shut...it never unloads, even when I first turn the compressor on and there is no/low oil pressure.

I've taken the cap off on the unloaded that's on top of the head, and everything seems to be moving freely...nothings stuck.

Can someone give me some ideas on what could be wrong with it?

Thanks!!

I have a 5hp Quincy 325 air compressor on an 80gallon horizontal tank. I rebuilt it several years ago....and it's always worked great. Just recently the unloader system on it has stopped working.The way it's supposed to work is that when you first turn on the air compressor there is a valve on the high pressure side of the compressor that is held open to unload the pressure until the oil pressure builds to a certain level, then the valve is closed, and the compressor starts building pressure.For some reason, my compressor is acting like the valve is stuck shut...it never unloads, even when I first turn the compressor on and there is no/low oil pressure.I've taken the cap off on the unloaded that's on top of the head, and everything seems to be moving freely...nothings stuck.Can someone give me some ideas on what could be wrong with it?Thanks!!