Central Pneumatic 94667r 3 hp electric oiled compressor

Google <make> <model> 1.5gal 6 hp central pneumatic compressor

Without seeing and being able to do hands-on trouble-shooting I can only make a shot-in-the dark analysis.

I, years ago had a similar situation, and it turned out that my compressor was one which REQUIRED LUBRICATING OIL IN THE CRANKCASE [just like a 4-cycle lawnmower engine].

I had failed to regularly check the oil level and over 4 or 5 years it had "used up" the oil and was beginning to run dry. Dry bearings build additional friction which will cause "drag" and slow the compressor RPM!!!!! That could explain the inability of your compressor to exceed 20 to 30 Psi!

With enough dry running, the bearings within the compressor will eventually totally wear out, and FREEZE-UP, locking the compressor up. Once that happens, the compressor will have to be replaced, OR OVERHAULED, just like you would do with a frozen bearing in a lawnmower engine!!!!!

IF, and I EMPHASIZE IF, RIGHT AWAY you properly lubricate the compressor [IF it uses crankcase oil] you MAY extend the life a little while longer, but that no cold start, and low high pressure capability suggest that the bearing(s) is/are dragging badly already.

If your compressor is an "oil-less" type, then an overhaul or replacement will probably be necessary.

Use soapy water to check for air leaks. Can also check piston ring and valves. Make sure engine is driving the compressor.

Does it have an intake air filter? Has the compressor been properly maintained? Oil less? It may have worn out rings and or valves

Possible that there is leak on the system or the piston/rings/cylinder has worn out.Also check for oil within the unit. Check the compression of the cycle and if this is too low it means that there is wear and tear and will require a overhauling and reset.

bad pressure regulator or regulator out of adjustment /or the contacts are sticking

if it is leaking air the check valve is bad.find the airline leaving the air pump follow this line to tank.this line attaches to the check valve which is screwed into tank.make sure no pressure is in tank when removing.

check and make sure that the valves do not leak

compressor will not build pressure

Check the pressure switch, they can become stuck in the open position. You can jump it to see if it is functioning or use a multimeter if you have one. Assuming that you've oiled and taken care of it it is unlikely that it simly quit, but that could happen... check across the poles of the motor for continuity which will tell you if the electric motor is blown. ALso make sure the compresor is not seized...