Given what you say, I'm inclined to agree with John: the engine problem is unrelated.
However, the engine does need 12v power to run. If the alternator fails, it runs until the chassis battery goes dea, then it quits. Usually takes 30 minutes or so, though. The dash lights dim and go ut along with the engine dying. Is that what happens?
What solenoid are you referring to? The engine has a solenoid to engage the starter, but you started it ok, so that must be good. Does your coach have a chassis battery disconnect solenoid?