Tools, Sharpening and Power Machinery - Air Compressor - craftsman - problem

I have a craftsman model 919-165050 5.5 hp 30gal oil less air compressor. It is 1999 vintage. It wont build more than 40lbs pressure. There does not appear to be any leaks preventing it from building pressure. I have the diagrams from the sears website. I cant seem to figure out what kind of screws hold the front shroud on. The front shround is the one that actually covers the compressor pump. There are two screws used. Also after I remove the head, where should I look for the most probable problem area. Thanks in advance.

are they torque screws? i believe that's what mine are. make sure your gauge is correct and regulator is working ok.

Chev72 - thanks -- yep they were T20 torx screws. The regulator seems ok -- no leaks of air. I cant think fo what else could be wrong with thie regulator.
I took the shields off. Nothing obvious seems to be broke.
I am about to remove the head and look at the internal parts. Any suggestions on what to look for ??

a diaphragm type unit? Or a fixed piston with a seal? In any case, these are the places to inspect for wear and tear in an oil-less compr. Replace as needed.

It is an oil less Craftsman compressor. After further inspection, the check valve is bad. It is not able to hold air in the tank. I removed it and cleaned it with carb cleaner however still not sealing properly. Also, preventing motor from starting when tank has some pressure in it. Also causing the following - when you shut unit off it tries to bleed off the entire tank pressure as opposed to just the line from the compressor to the tank. I called devilbess and ordered a new check valve as well as a rebuild kit for the compressor. Parts should be here in a week at which time I will dissasemble the compressor and rebuild.

the check valve usually creates a hammering sound but does not prevent full pressure. i does however make starting hard.
have you inspected the reed or popett valves in the head ?

Well, I rebuilt the compressor today and it did the same thing --would not pump more than 40psi. I dissasembled again only to find the middle metal reed valve on the exhaust side of the valve plate assy was broke in half. I cant believe I missed it when I dissasembled for rebuild. I called devilbiss but they were closed today. I will try again tomorrow to reach them. I hope I can order just the reed valve although the whole assy is only 20 bucks. Also replaced the defective check valve and the unit now holds pressure and I can now start the compressor with pressure in the tank as the unloader valve is now depressurizing just the line instead of the line and the whole tank.

Well, I received the new valve head assembly and installed it. I also removed the new piston, sleeve and connecting rod and put the old assembly back in as there did not really appear to be anything wrong with it. I fired her up and she came up to 120psi and shut off just like it was supposed to. Drained the air and she cut in around 90-95 right where she was supposed to. Realized I had a air leak somewhere. Got out the soapy water and found the regulator leaking. I dissasembled and cleaned, put it back together, tightened it up and it worked fine -- no leaks. I put the new piston, sleeve, connecting rod assembly in my closet in case I should ever need it down the road. I now have a total of $150 in the unit including purchase of $51. The bad parts were the check valve $17 + shipping and valve head assy $36.44 including shipping. The sleeve, piston and connecting rod was $35 + shipping. I really wanted to do this for aorund $100 and would have acccomplished that had I done a proper inspection before I ordered the parts. The one time I didnt follow procedure burned me. Anyway I have a real good compressor now and certainly learned a lot during the process.

You did good. If you can, put a filter upstream of the regulator. Otherwise, it'll gum up again real soon.