Craftsman air compressor woes

[scbdub]

Craftsman 3 h.p. 20 gal. model no. 919.176730 runs up to 100 psi and cut off normally but only if tank pressure is less than 40 psi. That is, at normal operating cut-in of around 80 psi it stalls and trip the circuit breaker. I have replaced the check valve and all 4 flapper valves without fixing the problem.

Can someone tell me how to make this compressor work properly?

 

[HotelMike]

Check the unloader. It should release pressure from the pump side when it cuts out. It's in the same box with the pressure switch.

If you have 100psi in the line from the compressor. The motor won't get enough starting momentum.

 

[The Cobbler]

motor start capacitor could be to blame too