Craftsman air compressor not reaching pressure

Just bought a Craftsman 3.5 HP 25 gallon (model no 919.155732) used from someone. It is an oiless, direct drive type thing.

It's supposed to reach 125 PSI and it only reaches about 55 or 60 PSI. From what I have been reading, it is most likely the O-rings in the compressor. How many O-rings are there? I found one that is around the metal pipe that connects the compressor with the tank as it enters the compressor. There is a large thin ring around the top part of the compressor around the flap valve (is that what it's called?) which seals the round cylindrical chamber that i guess makes up the walls of the piston.

Then there is a flat round metal plate that goes up and down (the piston itself?) which has a thin metal rim around it. Is there supposed to be another O-ring in there? There is a little gap between the round plate and the metal rim that looks about as wide as an O-ring might be.

Anyways, does anyone know how to find the part numbers? I was thinking of ordering from devilbiss rather than going to Sears, but I can't figure out what the part numbers are because there aren't any pictures/diagrams that I can find.

 

I have a similar unit--15 gal tank.
This thing is so loud the neighbors complain when I turn it on.
Your pressure switch may be turning unit off too early??
I'm waiting for mine to break down so I get a 220V oil unit & have some quiet..............
Some parts are available at Sears.

 

Welcome to the forums!

Does it shut off when it reaches 60 psi? or does it keep running with air leaking?

 

Well, went to the Sears store to look at the parts to see what they are supposed to look like. After I saw how tightly the piston is supposed to fit inside the sleeve, I realized both completely worn out.

Bought they kit to replace those parts and now it works like a charm.

 

Quote:

Originally Posted by mudphud

Well, went to the Sears store to look at the parts to see what they are supposed to look like. After I saw how tightly the piston is supposed to fit inside the sleeve, I realized both completely worn out.

Bought they kit to replace those parts and now it works like a charm.

I have the same problem with the same compressor. After reading the previous post, I replaced the piston/rod/ring assembly, now the compressor will charge up to 60 lbs, but not higher, and it just keeps running, and there is not any air leaking.

 

Tighten the water drain on bottom of unit w/ a pair of pliers.
See if it make any fifference.....................

 

The drain is tight, and all of the connections are tight, there isn't any air leaking. My next step is to replace the regulator.