OK, that is good to know that 3 phase circuits are working properly.
What is history on this unit you recently purchased? Have you ever seen it run properly with 1 phase 120/240 voltages before?
Have you performed the inspections recommended in the referenced thread regarding the interiors of the "AC Redistribution box" and "Control Panel box"? Any burnt, discolored, or otherwise detached wires? Any burnt/arced pins in connectors? Any components missing or looking like they overheated? Certain things need to be ruled out before specific troubleshooting can be applied.
Also, have you downloaded the TM's and begun reading them yet? Becoming familiar with the workings of the genset helps us help you. In general, how comfortable are you working on electro-mechanical devices?