Ahh... it's good to share additional information, now then assuming that you have the compressor and only the compressor by itself plugged into a test cord, and If you haven't done so already, remove the compressors little terminal cover & remove and inspect the start/run relay & the overload "Clikit" for any remaining dirt, wet spiderwebs/egg sacks, & anything else that could bridge the gap between the terminals of the unit or short them to ground (the metal case of the compressor) if it's got one, don't forget the starting capacitor too.
Then take a digital volt meter on the high-Ohms scale & test every terminal to the case of the compressor
( don't get your fingers across the meters test probes as it will give you a false reading) any terminal that doesn't read infinity (open resistance) to the compressors case indicates a short to ground & then it's time for a new compressor. have fun!
PS; so what kind of machine is this anyway?