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quincy 310 compressor unloader problem

 
  #1  
Old 11-25-2017, 01:13 PM
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quincy 310 compressor unloader problem

Iíve got a Quincy 310 roc 24 compressor that just started giving me trouble.... unloader is doing just that... and it wonít build pressure... worked fine yesterday, today it just blew me off...literally.
Oil level is full... pressure is 20 psi. Iíve taken the unloader apart and everything is moving freely and shows no abnormal wear... but something isnít moving to close off the unloader, I guess...

Quincy tech told me the check valve was the problem... took it apart and sure enough... washer was in pieces, so no seal. ordered/installed new duplicate check valve and problem is still there... so I'm backing up the pipe to the unloader valve on top of the compressor head...

it's connected to a 'pilot' valve on the side of the compressor by 1/4" tubing and the pilot valve is fed by 1/4" tubing from below the check valve (tank i/p) when I disconnect the line between the pilot valve and the unloader
I feel air pressure at the unloader end of the tube and the unloader closes and it will build pressure...so it should be getting a Ďsignalí to stop unloading, right ???

any quincy guruís or can someone help me trouble shoot this problem ??

anyone... anyone ????

john
 
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  #2  
Old 11-25-2017, 01:55 PM
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I can take a semi-educated crack at this one. The brass valve in the last picture (labeled "pilot valve") is the hydraulic unloader. It works off of oil pressure, it allows air pressure to recirculate back to the pneumatic unloader (the big mushroom valve on top) and hold it open until oil pressure builds up to operating level (not sure what the trip point is, 20psi maybe?). The fact that you're getting air pressure at the line to the pneumatic unloader (mushroom valve) means that the hydraulic unloader isn't closing, which means you've either got low oil pressure or a faulty hydraulic unloader valve.

Take the hex head plug out in the middle of the hydraulic unloader, there should be a spool and spring under there. Keep in mind how and in what order it all comes out or take a picture. Check the seals on the spool.
 
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Old 11-25-2017, 02:07 PM
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Also, check the locknut on this screw (red arrow). It's your oil pressure adjustment screw. If the locknut is loose, the oil pressure adjustment can vibrate and back off until you get below the low oil pressure setpoint for the hydraulic unloader valve, at which point the compressor won't load anymore.


 
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Old 11-25-2017, 08:31 PM
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Brownac... lock nut is tight and oil pressure is steady at 20 #.. I've tried adjusting it between 15 and 25 with no change ... can I remove the hydraulic unloader valve without draining the case ?? or is it below oil level...

would be easier to take it apart for inspection on the bench instead of mounted...

thanks for the info
 
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Old 11-25-2017, 08:45 PM
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Originally Posted by jniolon View Post
Brownac... lock nut is tight and oil pressure is steady at 20 #.. I've tried adjusting it between 15 and 25 with no change ... can I remove the hydraulic unloader valve without draining the case ?? or is it below oil level...

would be easier to take it apart for inspection on the bench instead of mounted...

thanks for the info
It should be well above oil level, just make sure you don't start the motor with it off or you'll have a mess.
 
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Old 11-25-2017, 09:04 PM
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Look for parts 9, 6, 5, or 4 to be stuck, or for bad seal at part 3. The most likely scenario is that part 9 is stuck and needs cleaning.
Don't use these part numbers to order anything, this is for a 325 and may or may not be your exact valve.

 
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Old 11-25-2017, 09:14 PM
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Originally Posted by Brownac1983 View Post
Look for parts 9, 6, 5, or 4 to be stuck, or for bad seal at part 3. The most likely scenario is that part 9 is stuck and needs cleaning.
Don't use these part numbers to order anything, this is for a 325 and may or may not be your exact valve.

so, I'm assuming 6,9,10 come out thru the cap opening and
4,5,6 come out after driving the roll pin out ???
or does the piston assembly complete come off after removing the roll pin and I'll have access to 4,5,6 ?

do you know if quincy dealers can still get a rebuild kit for this valve ??
 
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Old 11-25-2017, 09:32 PM
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9 and 10 come out with the cap. 6 should also come out with the cap if you have a fine pair of tweezers to grab it with.

I wouldn't mess with driving the roll pin out. If 4 or 5 appear to be stuck, spray some brake cleaner through it. The only reason you might need to drive the roll pin out is if 6 is stuck and you have to punch it out from the rear.

Quincy should still be able to get the kit. You can also get them on Ebay. I doubt they're OEM quality but they work.

There's a very good chance that your problem can be solved simply by cleaning part 9 and the bore that it rides in.
 
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Old 11-25-2017, 09:36 PM
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thanks... I'll try the cleaning step first.. just bought two cans of brake cleaner !!

john
 
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Old 11-25-2017, 09:44 PM
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I did a little research, it appears that the diagram above should be your valve. It appears that the model 7970x hydraulic unloader was used on the 308-350 compressors. If cleaning part 9 doesn't fix it, get a p/n 8063 rebuild kit.
 
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Old 11-25-2017, 09:45 PM
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It goes without saying, but make sure the valve is free and dry of any brake cleaner before you reassemble it, and don't spray any in the lines, on the off chance of turning your compressor into an engine.
 
  #12  
Old 11-26-2017, 03:46 PM
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well, pulled the valve today and it looks nice and shiney. When I undid the cap and carefully pulled it out followed by the spring ...looked in the bore and saw clean metal with a good coat of oil on the surfaces....the piston moved freely. When I took the piston out I found a small semi-circular piece of the rubber seal from the front of the piston... and what was still in the piston was deteriorated somewhat... looked rough and chewed up some... see pic... the push rod came out easily and was clean.. I gave the rod hole a shot of brake cleaner and let the assembly sit... I'm gonna order a rebuild kit on amazon/ebay and just replace everything... hopefully that will take care of anything I don't see. do you think the seal wear is what might cause the problem letting the air bypass ???

sorry for the poor picture, I couldn't get phone camera to focus that close

j
 
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Old 11-26-2017, 04:01 PM
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I believe that's your problem. A rebuild kit should fix it.
 
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Old 11-26-2017, 04:01 PM
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maybe a little better shot of the piston and the roughness of the seal is a little more apparent... and a shot of the bore
 
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Old 11-26-2017, 07:49 PM
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Your housing looks good. I think that piston seal was your issue.
 

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