The drain plug on my Porter Cable pancake compressor leaks so badly that it no longer build pressure. The compressor is just a little over 1 year old and I have always drained the compressor after each use. There were possible 1 or 2 exceptions when it sat for no more than 48 hours pressurized. Can I replace the drain plug on my own?

You can try a new capacitor, or test your existing one.
Plug its power cord directly to an outlet, no extensions, power lost in inapropiate power cords is also a probable cause.
Does the motor turn by hand or is it sticking?
One thing is an electric problem, another would be mechanical.

Yes use pipe thread seal. The center is turned to open and close no need to remove plug. If is frozen replace.

Most P/C compressors shut off at 150psi. If the pressure switch is bad, the pressure will rise until the safety pops. If the safety is not opening, then most likely the cylinder / piston ring is worn to the point that pressure will not increase past safety range (cylinder could be scratched near top ). If cylinder and piston are ok, then air is leaking somewhere (check all joints with soapy water). Good luck

The compressor has a max psi setting of 150.If the pressure is not reaching this or is only stabilizing at a low pressure you have an air leak around a gasket somewhere.If it is reaching 150psi and not shutting off your pressure switch is bad.Replace it.Check your owner's manual for a part number or go to www.factoryauthorizedoutlet.com to find the part.

i think you have a problem with the pressure control. unplug the compressor and open the controller. check all the connections and really look it over. these pressure switches today just do not hold up well. sometimes there is enough moisture in the unit that it can freeze over winter and crack. if yours has a plastic hose to connect then check that over as well. check this site. they have a good parts break down ans look ar parts 111and 112 and 113. all called pressure switch service kit.

http://www.ereplacementparts.com/porter-cable-cffn250n-type-compressor-parts-c-129_1662_3092.html

First take off the head on the air pump and check the reed valves on the valve plate. If they got hot and warped or cracked they'll work to a point then no more pressure can be built up. Next check the pistion ring and cylinder wall. If either is damaged you'll only get so much pressure build-up then it will leak past the piston.

I would check the reed valves in the pump. One of them may be broken.

The real question is where exactly is the leak coming from. Compressors have a pressure release valve designed to let the pressure off of the compressor motor so it can start when there is pressure in the tank. This valve is often the culprit and fairly easy to replace. You can order it direct from porter-cable online. Just in case double check the drain petcock sometimes these get worn and won't close completely and can easily be over looked when trouble shooting.

If this is a almost new compressor, check to see if the plastic plugs they install in the air intake has been totally removed. It is possible to run the compressor with plug still in place. You might have to remove the air filter to check.

most probably the one way valve in the heads unless the drain tap is opened