Quincy 308 air compressor help

[dimwolf]

I inherited this Quincy 308 air compressor and was told it would not work. I wired it up and to my surprise it started pumping air. It had a couple of pipes broken off in the tank so initially I could not really tell what it was doing. I got the broken pipes out and I decide to pull the head and see what kind of shape the compressor was in. I could not detect any wear in the cylinders and all the valves looked good. Everything back together and started it up. It took 45 minutes to build 150psi on an 80 gallon tank. Does anyone have any specs on this compressor? I emailed Quincy compressors but they haven't got back with me. There is one fitting on the back of the compressor that I can not figure out where it should connect (see picture) These are the facts I do know. Low pressure cylinder is 3” X 2 1/2” and high pressure cyclinder is 1 3/4” X 2 1/2” Electric motor is 3 hp 1750rpm and has a 4” pulley. The compressor has a 14” pulley and is running at 500 rpm. The pulley on the motor looks like it has been replaced. I am thinking that the pulley is too small I check the amps on the motor and there is not really any load on the motor. The serial number is 308 – 14 266365L Any help on this is greatly appreciated. I spent the last 2 nights on google with not much luck.

 

[Skin]

Whether or not the pulley size is off a bit 45 minutes to get to 150psi tells me its got valve issues or one huge leak.

 

[scott37300]

Are you talking about the short pipe in the 3rd picture with a cap on it when you say you don't know where it goes? That should be your oil drain.

 

[dimwolf]

The fitting just above the center of the crank

 

[Skin]

probably the centrifugal unloader. Is it leaking air while its running? It should have a tube running either to the head of the pump or to the check valve coming out of the tank. It unloads the pressure until the pump gets up to operating speed. I cant tell what its connected to in your pics.

I really common issue is the unloader getting stuck open or the check valve getting stuck open. The compressor will do exactly what yours is doing since its bleeding most of its air. It should be quite obvious, it would be making a loud hissing sound while running.

 

[dimwolf]

no leak while running....only when shut off...should I tee it in with the line that runs from the unloader valve to the control switch?

 

[Skin]

sorry i edited that post a bit. No, one side of the unloader should be open as it is, the bottom tube thats running out most likely should be running into the check valve. The pressure switch for the motor would trigger based off the tank pressure and is commonly hooked up along the main outlet.

pic for reference

Is the unloader functioning when it starts up? It would hiss briefly then stop as it closes. If you're certain the valves are okay, arent sticking, and nothing is broken [though it would surprise me given the filth on it] there must be a leak somewhere. Check valve leaks and the like dont exactly blast you with air, it just makes a leaking noise that grows progressively louder as pressure builds.

 

[dimwolf]

Thanks for the info I will do some more diagnostics on the unloader and post the results

 

[bmwpower]

This might help. Shouldn't that top fitting have a line running from the fitting to the unloader like mine?

 

[SurgeonGeneral]

If you didn't figure it out yet, you need a tube running to the unloader tower on the cylinder head. From the picture it seems that tube is missing.

 

[tacoman17]

Hello,
I am a new guy around here and I am trying to find out more about my Quincy air compressor.
The numbers on the tag read F308-2-7383-1
Can anyone tell me about it?How old it is and where I can get a manual for working on it. Complete overhaul parts etc.Any help would be greatly appreciated.

 

[mrpizza]

If you email quincy they are extremely helpful. They can send you parts books and manuals to help you out.

 

[Bran]

Hey y'all. Newbie here. Just got this old 308 26. Its definitely missing some tubing, but cant find much info on it. Any help on where to start would be greatly appreciated. Thanks.