This is from a prior post. My genset dies when we start the coach also...
It is good to know that someone else has experienced this same quirk. I feel better about that.....
The root cause of the generator shutting down that I am proposing, is not related to a charging issue from the generator. You are right that the generator primarily charges the house batteries via the Xantrex and that was all working fine. It is that the generator shares the chassis batteries with the C12, and while the generator is running it is monitoring itself and using some electronics to manage and control its operation (like over temp, low oil pressure, holding the fuel solenoid open and pumping fuel, etc.). While you are cranking the C12 my guess is that the 12V chassis battery wiring harness that provides the necessary continuous operating voltage that the generator requires drops to maybe 8 or 9V. During that interval, voltage wise, I am thinking that we dropped below the voltage operating window required by the generator electronics to sustain running and it shut itself down. The generator was running several hours and just died while cranking the C12 and then it restarted immediatly without any hesitation so my thinking is that this was not coincidence.....The shut down timing was just too perfect.
Later Ed