Hi,

Yes, you should feel it suck air - and it is a but pulsating because it's a reciprocating (piston) compressor. What you shouldn't feel is air moving back out.

Piston compressor that don't built over 50 psi typically have bad valves. Most of the time the outlet/exhaust valves. For some reason, the pressure stabilizes around 35-50 psi when this happens.

The inlet valves prevent the air from moving back out. The outlet valves make sure that the compressed air doesn't flow back into the cylinder.

With bad outlet valves, the semi-compressed air is simply moving back and forth between the cylinder and the outlet pipe. With bad inlet valves, the air moves back and forth from the cylinder to the inlet pipe/filter ... in both cases it's not really compressing the air.

Since you have a 3-stage unit, you need to figure out where (which stage) the problem is. What is the normal maximum pressure?

I would start with stage one, as that is the most likely source of the problem.

Good luck!

Cas