Try PinWiki if you haven't already, specifically under WPC problems and solutions. I've been lucky enough to avoid start up issues so far so don't have any hands on advice for you, but PinWiki usually at least gets me on the right track. 4.3 Power-On LEDs and Sound Tones (Bongs) should give you an idea where to start.
http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Jumpers.2C_RAM_and_ROM_size