quincy 325

[lance8615]

My quincy 325 isn't unloading properly. I replaced the hydraulic unloader which didn't help. After the unit builds pressure to 180 psi and shuts off, all I am getting is a slight escape of air thru the air filter but not the usual "whoosh" that it used to do. So it takes a long time until the flywheel is loose enough to turn easily for the next start up. Any ideas/suggestions on what to look for/repair/replace? Thanks! Lance

 

[MacMcMacmac]

Take the tops off the unloader towers and see if the diaphragms are split. If they are still intact and pliable, take them off and see if you can manually push down on the pucks underneath them. Sometimes condensation gets in there and corrodes the whole assembly tight.
Check to see if there is air coming out of the copper line to the towers when it shuts down. Just loosen off the ferrule and see if air rushes out after shut down. You can also disconnect this line and let the compressor cut in and blow air into the system with a blowgun to see if it actuates properly.

Make sure oil pressure drops to 0 after shutdown. There is a special valve in some 325 cranks that bleeds off oil pressure to allow the hydraulic unloader valve to cycle quicker. Some 325's just have a small hole drilled in the plug for the oil passage in the front of the crank to do the same thing, as well as squirt oil into the front bearing.

 

[lance8615]

Take the tops off the unloader towers and see if the diaphragms are split. If they are still intact and pliable, take them off and see if you can manually push down on the pucks underneath them. Sometimes condensation gets in there and corrodes the whole assembly tight.
Check to see if there is air coming out of the copper line to the towers when it shuts down. Just loosen off the ferrule and see if air rushes out after shut down. You can also disconnect this line and let the compressor cut in and blow air into the system with a blowgun to see if it actuates properly.

Make sure oil pressure drops to 0 after shutdown. There is a special valve in some 325 cranks that bleeds off oil pressure to allow the hydraulic unloader valve to cycle quicker. Some 325's just have a small hole drilled in the plug for the oil passage in the front of the crank to do the same thing, as well as squirt oil into the front bearing.

Thanks so much for replying. I'm away from home for a few days but i will get back on it soon. I did notice before that one of the pucks (high pressure suction) can only be pushed down a very small amount, maybe one or two mm. the other can be pressed down a good bit more. Also, I am confused as to when air pressure from the tank via the hydraulic unloader valve is delivered to the unloader towers...during running or after shut off (unloader phase) I wasn't sure about my hydraulic unloader which I think is from 1986 so I replaced it, no help. I have new pins and springs in the suction valves and I recently took them apart, cleaned, and reassembled with a touch of anti-seize. They move freely No difference. Having trouble understanding this problem as the compressor was running beautifully for years and just in the last few weeks has been acting up. Thanks again for your very sage suggestions/observations......best..Lance

 

[lance8615]

Thanks so much for replying. I'm away from home for a few days but i will get back on it soon. I did notice before that one of the pucks (high pressure suction) can only be pushed down a very small amount, maybe one or two mm. the other can be pressed down a good bit more. Also, I am confused as to when air pressure from the tank via the hydraulic unloader valve is delivered to the unloader towers...during running or after shut off (unloader phase) I wasn't sure about my hydraulic unloader which I think is from 1986 so I replaced it, no help. I have new pins and springs in the suction valves and I recently took them apart, cleaned, and reassembled with a touch of anti-seize. They move freely No difference. Having trouble understanding this problem as the compressor was running beautifully for years and just in the last few weeks has been acting up. Thanks again for your very sage suggestions/observations......best..Lance

Hi Mac, I was sick for a while and am just now getting back to the Quincy 325 which is not unloading. I did everything you suggested....diaphragms are good, also checked for air flow to the unloader towers; I'm getting strong air flow when the unit is off and no air flow when it is running (oil pressure 20 psi) So i took both towers apart and I don't see anything broken or missing. The little plungers and springs (3 in each valve) seem to move freely and when I compress them I can see the valve plate move away from its seat. Do you have any ideas or suggestions on where to go from here? I really appreciate any insights or suggestions.....thanks...Lance

 

[MacMcMacmac]

I'd check the vent line between the tower and the inlet to see if the tube hasn't been clogged up with debris.

 

[WagonHo!]

Take the tops off the unloader towers and see if the diaphragms are split. If they are still intact and pliable, take them off and see if you can manually push down on the pucks underneath them. Sometimes condensation gets in there and corrodes the whole assembly tight.
Check to see if there is air coming out of the copper line to the towers when it shuts down. Just loosen off the ferrule and see if air rushes out after shut down. You can also disconnect this line and let the compressor cut in and blow air into the system with a blowgun to see if it actuates properly.

Make sure oil pressure drops to 0 after shutdown. There is a special valve in some 325 cranks that bleeds off oil pressure to allow the hydraulic unloader valve to cycle quicker. Some 325's just have a small hole drilled in the plug for the oil passage in the front of the crank to do the same thing, as well as squirt oil into the front bearing.

you’re the guru of quincy compressors, learn something everytime you post.

 

[lance8615]

HI Mac, if you mean the coper line that goes from the unloader tower to the head, yes, it is open. I had another question (hope I am not wearing out my welcome)...when I got the unit about 6 yrs ago I rebuilt everthing, rings, bearings, seals, etc. At that time, I put a little "anti-seize" on the six pins and springs that go in the top of the intake pistons. Now I am wondering if the pins/springs are corroded or "stiff" because of congealed anti seize?? Seems remote but otherwise i am out of ideas. Any thoughts? Again, many thanks for your willingness to help. You don't know how much you depend on your compressor until it doesn't work...best....Joel

 

[MacMcMacmac]

I'd think at this point that the HP unloader isn't stroking fully or is corroded. They should both move the same amount. The short whoosh is probably the LP blowdown air. The HP sounds like it isn't blowing down much at all. Just remember to back off the threaded ring if you take off the valve cover so yo don't split the cover by torqueing it down against the ring.

 

[lance8615]

I'd think at this point that the HP unloader isn't stroking fully or is corroded. They should both move the same amount. The short whoosh is probably the LP blowdown air. The HP sounds like it isn't blowing down much at all. Just remember to back off the threaded ring if you take off the valve cover so yo don't split the cover by torqueing it down against the ring.

I found out that the HP unloader wasn't giving a full stroke, because the stem of the valve that sticks up and is capped by the "hockey puck" was for some strange reason too short and therefore no matter how much pressure was put on it via the diaphragm it wouldn't go down far enough to trip the unloader pins and springs (!) So I JB welded a little extension on the valve stem and now all is good. Thanks again for your help and advice......I am sure that other compressor owners have also benefitted from your expertise....best regards..Lance