How to install a big condenser?

I have this small compressor that I use with an airbrush. Its a medical
surplus of some kind. Its somewhat round with a fan at either end. When I
connect it to power I hear a loud humming sound and the compressor won't run
unless I spin one of the fans by hand, then it works fine.
I think installing a big condenser should make it work without having to
spin the blade by hand. How is such a condenser installed and what value?
Thanks in advance for your help. Bob

 

A condenser (capacitor) can be used, only if the motor is wound as a
capacitor run motor. If not, there is some other mechanism to produce
torque when stalled (a start winding that is switched out by a
centrifugal switch once the speed gets up) or pole shading copper bars
that enclose part of each field pole. Perhaps you can send a picture
or two of the motor, especially what it looks like with an end bell
removed. You need to understand how it was intended ot start before
you try to reinvent it. Perhaps it contains a defective starting
capacitor that you just have to replace.

Does your motor look like any of these?
http://www.engin.umich.edu/labs/csdl/ME350/motors/ac/induction/1-phase/