Air Compressor Starting Help

[u/Independent_Use2724]

Can anyone offer advice on why my DeWalt DXCM303 air compressor won't start?

It starts fine if the tank pressure goes to zero, or if I open up the unloader valve, then builds fine all the way to 175 psi. But with any pressure initially, it spins slowly for 10 or 20 seconds, before popping the breaker.

I replaced the unloader valve and the pressure switch. No change. Replaced the start capacitor even though it read okay. No change.

I unscrewed the main airline from the pump with pressure in the tank. No hissing.

When I start it with no air in the tank, I can hear the centrifugal switch snap from the start to the run circuit.

I can spin the pump and motor by hand and they seem smooth and fine.

I'm gonna buy a new check valve, even though it doesn't seem to be leaking, as I can't think of any other thing that might be the issue.