I have a Craftsman model 919.152932 33 gal horizontal tank, 6 hp oiless Air Compressor. The compressor started to run for extended periods before it would build up to cut off pressure. Now the compressure will not build pressure. The motor seems to be running fine and I can't detect any leaks.

remove shroud and see if fan is broken but may be piston is shot

i would look at the head gasket

Sources of noise from craftsman oil free compressors (could be Made by Campbell Hausfeld or Porter Cable) include loose fan, failing bearing/s on the piston rod and housing, failing seal ring on piston, air filter intake and loose motor mounts. With the housing cover off, check the fan blade for cracks or loose screw. Turn motor by hand till the piston is at top of stroke. Examine the cylinder for scratches close to top. If scratched, air is leaking past vinyl ring making noise and causing longer fill time. If everything looks ok, suspect noise coming from bearings. Hard to tell if bearings are failing by looking at them. I have seen many failures of the piston bearing on the crank (fairly easy to change, I use alternator bearing from auto parts ) , however, the bearing in the housing just behind the crank bearing is much harder to replacable. Good luck with your fix-it project.

Some of the craftsmen compressors have pistons that are coated on the top of the dome. Once the coating wears off, they have severe loud piston slap. If you continue to run it the way it is, it will snap the connecting rod in half or break the piston and possibly the cylinder.

This product manual will show the exploded view on how it comes apart/goes together:
http://c.shld.net/assets/own/00915216e.pdf

If there is pressure at the pump, either:

1) The tank check valve isn't opening (it's located where the line from the head enters the tank - usually extends into the tank, and the the pressure switch unloader line comes off of it as well)
2) The pressure switch unloader is bleeding off the air. This is a small valve on the side of the pressure switch. It should close when the compressor is running and open when the compressor shuts off to bleed off head pressure.

Dismentl the valve plate check the gaskets and the valves,cif not good change and it wlii be ok

Its best to use a 30wt non detergant

check your popoff valve first. it is the valve with the ring hanging on it. You will hear the air rushing.

If you don't hear any air rushing, you may have fried the piston rings or broke/chipped the piston(not your fault)..especially with oiless compressors

Sound like the fly wheel is loose or belt is the same