How much pressure are you getting?

It should shut off at about 140 psi.

Is it blowing the safty valve?

The air gauge by the pressure switch goes above 200psi which is normal for this compressor.I replaced the pressure switch and that was not the problem,it still wont shut off.

Hi Brutus. I recently had a customer with the same problem. He tried replacing the pressure switch too but it didn't fix the problem. The faulty part actually ended up being the check valve. It's figure #11 on this diagram:

Porter-Cable C3551 Compressor

I would inspect the valve to see if it's operating properly. If not, here is a link to the valve information page:

Porter-Cable Check Valve #D29280

Thanks I'll check out the check valve ,let you know if that is the problem!

I have a somewhat similar problem, only my compressor ( model C2001-wk ) will only go to 87psi and won't shut off. It does not lose pressure when I shut it off and I have it adjusted to maximum pressure. It gets to about 87psi and stays there no matter how long it runs Any ideas?

Hey grockett,
You may have the piston and sleeve starting to wear out..item #106..part # KK-4964..
available at ereplacementparts.com... this is a typical problem for most of the oil-less air compressors..they just wear out over time from use..you also may have a valve plate assy problem..but once you get into the piston..you will be able to see the wear quite clearly..
hope this helps..:)
Craig

I am having the same issue with my compressor. It hums but the motor wont run. Any ideas?

Kevin

It sounds like your not getting enough power. Do you know what gauge your wireing is? Are you using a extention cord? Maybe you could try it on an outlet at your neibors. in my house it's wired with 14ga and mine wouldn't run. When I wired my shop I used 12ga and had no problems. good luck let me know if you have any questions.