Quincy 355 ROC 12 Randomly Unloading

[InjectorService]

Hey Guys, I have a 325 Quincy setup that is giving me grief. A few things are going on. It leaks out the intake, leaks oil, and now it started randomly unloading. I have checked the oil level and it looks good, about the middle of the dipstick.

I know the leaking out the intake is caused by one of the valves, I took them all apart and tried to level them, but obviously I didn't do a good enough job, its better, but still leaks.

The oil leak I can look after. It was a slow leak, and then I tightened the bolts, but now its a fast leak. Again I can look after this, no problem.

But the thing that really bugs me is it is randomly unloading. It will get to about 100 psi and all of a sudden will unload. Then it will pump again, and then unload. at about 120 psi, it stays loaded until the 160 psi shut off.

Also where is the go to place for Quincy parts in Canada?

Thanks in advance guys!

 

[InjectorService]

Someone's got to have some idea! Come on guys!

 

[tre873]

I wonder if the check valve in the tank is randomly sticking open and allowing the pressure to back-feed through the valves. Or possibly the relief valve randomly opening?

 

[My Old Tools]

Check over at owwm.org. One of the boards I frequent has knowledgeable people on Quincy compressors and I think it is there.

 

[LS6 Tommy]

The unloader is hydraulic. Fix the oil leak first. The unloader issue may stop.

Tommy

 

[fitter30]

Don't see a check in the discharge line to tank so it's using the valve reeds to hold pressure back. Pull the head check the valves add a spring check. Pull the air cleaner block air intake see if the compressor knocks if it knocks rod problems.

 

[MacMcMacmac]

Pull the hydraulic unloader and replace the seals.

 

[InjectorService]

Check over at owwm.org. One of the boards I frequent has knowledgeable people on Quincy compressors and I think it is there.

I will definitely check these guys out. I thought this would be the go to place.

The unloader is hydraulic. Fix the oil leak first. The unloader issue may stop.

Tommy

This was my thoughts too. There were 2 extremely small leaks. I tightened the screws to the cover on 1 leak and it stopped, tightened the bolts on the other cover and they got WAY worse. I'll do this before continuing.

Don't see a check in the discharge line to tank so it's using the valve reeds to hold pressure back. Pull the head check the valves add a spring check. Pull the air cleaner block air intake see if the compressor knocks if it knocks rod problems.

So from what I read here I shoukd have a check valve on the discharge line into the tank? This is news to me, I will definitely do that. I have pulled the head, the valves all look good, but obviously one is still leaking back. Would this contribute to my unloading problem, or only my leaking through the intake problem?

Pull the hydraulic unloader and replace the seals.

I can definitely do this as well, are you talking about the towers on top or is there something else?

 

[MacMcMacmac]

It is the brass valve on the side of the crankcase that has the air line going in and out of it. There are two rubber cup seals, or a cup seal and an x-ring that trap oil pressure and actuate the plunger valve that supplies and cuts off air to the unloader towers. If the rings are sealing poorly the unloader operation may be erratic. Did you check your oil level recently? Is oil pressure consistent? What is the pressure set at?

 

[TonyJ]

I second the check your oil pressure and see if it is being consistent while running and if it is dropping see if it’s unloading at the same time it drops.


Tony

 

[InjectorService]

If I recall the pressure stays at 10psi even when unloading. It builds oil pressure quite quickly upon startup. I'll double check tomorrow though I'm going off of memory. Also this is on the 55 year old oil pressure gauge, so it might not read 100%. Also one of the oil leaks is coming from that valve so I think you guys are definitely pointing in the right direction

 

[TonyJ]

10 is low. Adjust the oil pressure up to around 20 and see if it acts normal then. When looking at the back to the left of the pressure gauge there is a bolt with a lock nut. Loosen the lock nut and tighten the bolt while the compressor is running and when you get to 20 psi tighten the lock nut. It doesn’t take much turn to raise or lower the oil psi. The idea is when the pump has low or no oil pressure it causes the unloaders to unload and that is seeming to be where your main problem is


Tony

 

[TonyJ]

Manual says 15 psi but tech support will tell you 15-20psi. Better to be on the upper end than the lower lol


Tony

 

[TonyJ]

That I circled is the adjustment on your pump


Tony

 

[InjectorService]

Thats awesome, thanks guys Ill try to get to that this week and report back. I've been super busy lately, and right now I have another project that needs more attention.
AKA My Vette is stuck on my icy driveway, haha!

 

[InjectorService]

Ok so I decided to swap projects. The car is in the yard, the compressor is apart. One leak is this cover I removed, the other is coming from one of the copper lines to this unloader valve. I'm not sure how that valve is supposed to work, obviously something is supposed to move though. Anything I should look for while I have this big cover off?

 

[TonyJ]

No oil should go up the line to the unloaders. That valve you removed works off of oil pressure to open and close. The lines that connect feeds the tank air to the unloaders when the oil pressure is high enough. So if your getting oil in the line going to the unloaders then the seals in that valve needs replaced. Also there is felt and screens down inside the ports where the lines connects to that valve so make sure those are also cleaned while your already there


Tony

 

[TonyJ]

I have a Quincy 230 which is basically the same as your 325 except yours is 2 stage and mine is single stage. Allot of the parts will interchange between mine and yours. They even share the same crankshaft lol


Tony

 

[TonyJ]

Nothing really to check for while the cover is off except for maybe cleaning out the sump and checking for play in the rod bearing and end bearings


Tony

 

[TonyJ]

Tony

 

[InjectorService]

Thanks Tony for all the help I really appreciate it. I'm going to go ahead and replace the seals in the unloader, and rebuild the towers too so I can stop the leaking back. But I need to order the parts.

Do you know a good place in Canada to order Quincy parts? Theres no one anywhere near me that deals in it. I could order from the US too, but the one place I tried to buy from wanted to charge me $110US for shipping which is absurd.

Edit, I think the unloader is working correctly as there was no oil in the lines themselves, but the O-Ring on top pictured is leaking.

 

[TonyJ]

I usually just get my parts from eBay. You can get the part numbers from the page I posted. Also if you end up taking the check valves out when you take the unloadeders off then it’s recommended to replace the copper crush washers that’s under them. And you will need a tool to torque the valves back down. I made the tool out of a socket and just used my torque wrench when I did mine


Tony

 

[MacMcMacmac]

Before I would pull the valves, I'd go to a hydraulic shop and get a pair of replacement x-rings for the unloader valve and try it out. Remember, it is a hydraulic valve, so it is going to react instantly to any pressure drop due to a leak, which sounds like your problem exactly. Once you take the valves out you are creating another pile of work for yourself that may be completely unnecessary. I second increasing the oil pressure, although i have seen 325s running happily for years with 7psi

I once had a screw compressor that the owner complained would blow the safety valve, except by the time we arrived to fix things it would be running normally. The amount of heat in the compressor from running let the seals in the inlet valve actuator expand enough to keep the control air inside where it belonged, but after sitting all night they would shrink back enough to where it could not hold air, and the inlet valve would not actuate and pressure would run away. Your seals sound like they are on the bitter edge of working, just like those were.

If your interstage safety valve is not popping, your valves are likely just fine. You can screw a 100 psi gauge in there while its running and see if there is a good steady pressure in the interstage, around 30-40 psi if I remember correctly, and without the needle jumping around erratically. If the pressure is very low, you have low pressure cylinder valve problems, if it is at output pressure, you have high pressure cylinder valve problems.

 

[InjectorService]

Before I would pull the valves, I'd go to a hydraulic shop and get a pair of replacement x-rings for the unloader valve and try it out. Remember, it is a hydraulic valve, so it is going to react instantly to any pressure drop due to a leak, which sounds like your problem exactly. Once you take the valves out you are creating another pile of work for yourself that may be completely unnecessary. I second increasing the oil pressure, although i have seen 325s running happily for years with 7psi

I once had a screw compressor that the owner complained would blow the safety valve, except by the time we arrived to fix things it would be running normally. The amount of heat in the compressor from running let the seals in the inlet valve actuator expand enough to keep the control air inside where it belonged, but after sitting all night they would shrink back enough to where it could not hold air, and the inlet valve would not actuate and pressure would run away. Your seals sound like they are on the bitter edge of working, just like those were.

If your interstage safety valve is not popping, your valves are likely just fine. You can screw a 100 psi gauge in there while its running and see if there is a good steady pressure in the interstage, around 30-40 psi if I remember correctly, and without the needle jumping around erratically. If the pressure is very low, you have low pressure cylinder valve problems, if it is at output pressure, you have high pressure cylinder valve problems.

Thanks, Ill see if I can get some new "X" rings. IT does sound like the exact problem. It will run great at startup, and then start unloading around 100psi, and then suddenly it starts again. It might just loose a bit of pressure and then heat up and expand. It doesn't help my shop is around freezing temperatures right now.

I don't fully follow the interchange testing thing, but maybe it will become more apparent when I start looking at the actual compressor.


ON ANOTHER NOTE: What sort of intake filter do I want to buy for this thing. Whoever had it last has some sort of junk that looks like it is made from furnace ducting on there, I want to buy a nice filter that offers filtration and quiet running.

 

[MacMcMacmac]

Thanks, Ill see if I can get some new "X" rings. IT does sound like the exact problem. It will run great at startup, and then start unloading around 100psi, and then suddenly it starts again. It might just loose a bit of pressure and then heat up and expand. It doesn't help my shop is around freezing temperatures right now.

I don't fully follow the interchange testing thing, but maybe it will become more apparent when I start looking at the actual compressor.


ON ANOTHER NOTE: What sort of intake filter do I want to buy for this thing. Whoever had it last has some sort of junk that looks like it is made from furnace ducting on there, I want to buy a nice filter that offers filtration and quiet running.

Solberg filters are good quality, but put something on there that you can readily get filter elements for. If there is a compressor shop nearby they probably have something on the shelf. Its just a NPT port, so the possibilities are vast.

I called them x-rings, but the proper name is quad rings. I just get them confused with the x rings in a motorcycle chain sometimes.

The leaky seals may be contributing to the low oil pressure as well. One problem may be exacerbating the other.

 

[InjectorService]

Solberg filters are good quality, but put something on there that you can readily get filter elements for. If there is a compressor shop nearby they probably have something on the shelf. Its just a NPT port, so the possibilities are vast.

I called them x-rings, but the proper name is quad rings. I just get them confused with the x rings in a motorcycle chain sometimes.

The leaky seals may be contributing to the low oil pressure as well. One problem may be exacerbating the other.

Thanks, there's not much for compressor shops out my way, I'm most likely going to order some stuff online tonight and see how it turns out for me.