I have been reading an excerpt from the C-160 flight manual I found online, and I was reading that the engine starters have an air inlet to them which leads me to believe the engines are pneumatically started as opposed to electrically started.  I can start both engines with the APU bleed valve off.  Also, does anyone the difference between the APU bleed valve and the APU Compressor Output Valve? 

                                                                                                                             Alan