Air compressor problem

682bear

H-M Supporter - Gold Member
H-M Supporter Gold Member
Joined
Nov 28, 2016
Messages
2,243
I looked at an air compressor that is for sale this morning. It is a Porter Cable 80 gallon 2 stage, model # CPLKC7080V2. We checked the oil and turned it on. The seller said thats the first time its been powered up in at least 10 years.

We let it run about 5 minutes, it was pumping air, but, in my opinion, way too slowly. In 5 minutes, the pressure pumped up to around 100 psi. The compressor is rated at 175 psi... I'm guessing 10 minutes or more to reach shutoff, maybe?

It didn't appear (to my highly calibrated 'eyeball tachometer') to be turning the 3450 RPMs that the tag on the motor claimed... maybe half that...

Also, I removed the pulley guard and turned the pump by hand, and could not feel hardly any compression... but I'm not sure how much compression should be felt in a compressor pump.

It was pushing a good bit of air out of the crankcase breather... more than I thought it should...

Not being a compressor expert, I decided that I didn't feel comfortable paying the $500 he was asking... at least without doing a little research first.

Any ideas, opinions, or info is appreciated.

-Bear
 
I sounds like the pump is just worn out and needs a rebuild. If the motor is running slowly with a worn out pump, it's no good either. Keep looking.
 
I have 2 stage Gardner Denver the rpm is around 750 so I don't think you should expect 3450rpm. As Nogoingback suggested keep looking. sounds like rebuild time
 
If I owned it... and If it hasn't been run in 10 years...Quite possible that a piece of trash or rust scale may be keeping a read valve open. If you can pull the valves off without pulling the head...I'd do that lickedy split. Check valve seats / reed valves.

But...I would do as others advise and keep looking. A tank sitting for 10 years with a closed drain valve will still build moisture from condensation. The tank may also be rusted on the inside.
 
Yeah, I have already passed on it, but it is a friend of mine that is trying to sell it, so I'm trying to get some ideas about what may be wrong with it to help him out.

I sort of had an idea that a valve may be stuck open, but I've never been inside a compressor pump, so I'm not sure exactly how they are built.

-Bear
 
Yeah, I have already passed on it, but it is a friend of mine that is trying to sell it, so I'm trying to get some ideas about what may be wrong with it to help him out.

I sort of had an idea that a valve may be stuck open, but I've never been inside a compressor pump, so I'm not sure exactly how they are built.

-Bear
Most of the compressors I've had were designed so the reed valves could be accessed fairly easily. Usually some sort of plate or a nut which you could remove fairly simply. Check out the diagram of the compressor in this link. Like I said..It may very well might be a bad reed valve (cracked disc) or a piece of trash in the valve. https://servicenet.dewalt.com/docum...nual/Porter-Cable/200-2882-A,PXCMV5248069.pdf

Numbers 15, 16, 17, 18 are the valves on page 24
 
It's a slippery slope with all old machines, your friend may invest money in rebuild and never get them back after the sale, if is in good shape sale it as is or just scrap it.
 
If it was a single stage it may take that long but two stage should have done it in 5-6 minutes . Did you bleed it off to see if it came back on and how long it took to rebuild pressure ? , When you do get one plumb a drain line out where you can blow out the moisture DAILY, I USED A 1/4 pipe ball valve and black iron pipe for mine it's now about thirty years old.
 
If your even thinking about using a compressor that has been sitting for 'at least 10 years" . And it ran fine my first thing to do would be check out that tank carefully. Compressor tanks don't like sitting with water in them that long. I agree on the possibility of the valves being crudded up. Another is stuck rings Even one would affect the pumping.
 
Back
Top