Sick Quincy 325, Please Help Diagnose

[bad_idea]

I have owned this Quincy 325 ROC 7 for about two years now. Use it in my home garage infrequently. I last used it about two months ago, have been out of town for work. I fired it up this morning and it will not exceed 30PSI. It spools up slowly because I have it on a VFD that ramps the frequency up slowly. Can someone point me in the direction to tear into it? Thanks.

 

[W-Cummins]

Well it kinda sounds like its got the dreaded small end rod knock, but that is not going to make it only pump up to 30psi. Check the unloaders and or the valves for the problem.

 

[bad_idea]

Ohh boy. Rod knock and valve issues. Fair to say it's going to need a full rebuild?

 

[Wrench97]

Is it building oil pressure?

 

[gimpyrobb]

Also, inspect the check valve. They can go bad or just get plugged with turds.

 

[W-Cummins]

Ohh boy. Rod knock and valve issues. Fair to say it's going to need a full rebuild?

I'm not positive about the rod knock, but it kind of sounds like mine did with it... Also you can change out the rod and put a new small end bushing in it ( in mine the piston was trashed with more than 1/4" of play!! so I needed to replace it), with out a complete reman if the other stuff is ok



Is it building oil pressure?


It must be at least for long enough to pump up to 30 psi as the hydraulic unloader will not turn on if there is not enough oil pressure.

 

[bad_idea]

Oil pressure is reading good on the gauge.

 

[seber]

It sounds normal for that model. Mine sounded the same for thirty years. But I can hear the air escaping. Move a draped strip of paper around it and see if you can locate where it is blowing from.

 

[jmdirk]

Leaking somewhere, head gasket or reed valves would be my guesses

 

[Shoreline_]

Also, inspect the check valve. They can go bad or just get plugged with turds.

There doesn't need to be a check valve so the OP can remove it if he wants.

 

[TeenagerThatLikesFloorjac]

Interesting, 30-40psi is where the unloader valve starts to function and unloads air if theres no oil pressure. You clearly have oil pressure and you can't hear any air leaking from the unloader. So that doesn't seem like an issue.

I suspect an issue with the valves. Remove and inspect the air filter. Put your palm over the port. It should **** onto it, if it's pushing and pulling there's definitely a valve issue. You can do the same at the discharge. Don't wear nitrile gloves or anything similar, it might **** a chunk into the head... ask me how i know

 

[gimpyrobb]

There doesn't need to be a check valve so the OP can remove it if he wants.

Why not? I only ask cause I have one that has a check valve.

 

[Shoreline_]

Why not? I only ask cause I have one that has a check valve.

In tank check valves are one way for unloaded starts. Since the Quincy uses a mechanism that holds open the intake valves (on qr series) it doesn't need to drain the discharge tube. Once it builds oil pressure and releases the intake valves, usually the pump is pretty close to speed. The discharge valves are the check valve to the service line / receiver.

I don't use tank check valves on my qr pumps. They run fine.

 

[MacMcMacmac]

Sounds like the compressor is loading properly, but you can unscrew the Swagelok fitting at the first tower and see if there is still air coming through the tube.

Pull the interstage safety valve and put a decent gauge in there and see if you get a good constant pressure around 30-40psi. If it's jumping all over the place you have valve issues.

Sometimes the head gasket fails between the cylinders and the air gets passed back and forth between them after a certain pressure is reached.

Seized unloader in the hp cylinder?

Loose valve?