The readings you've gotten at the compressors' wiring terminals seem just fine, the top connector is the Common, the lower left is the Start winding, & the lower right is the Run winding.
there is no way to test the original start-run relay, as it's a current driven (controlled) device & it needs an electrical load to function ( the compressor windings themselves in this case)
Now is the time to replace the original start-run relay with an elctronic 3-in-1 starter/booster unit. ( or they also make a standard elctronic plain start-run relay) that will have 3 long color coded wires to attach to the compressors pins, white=start, black=common, & red=run. check online at Grainger.com uder the Supco brandname. you'll need the model rated for 1/5 to 1/4 H.P compressors (H.P.=horespower)
if the compressor still wont start with the 3-in-1 booster installed, then it's time for some service work on the bugger.
Also note, with a grain of salt, that these machines are 20<-->50 years old & you may get a few more years of service out of the original compressor, or only a few more minutes! the old 60-feet or sixty seconds warranty applies here. whichever comes first.
so start running!
Hope this helps. JohnieG
