We have the 611 in our rig. You can definitely hear the burner firing when using propane. But just because it is firing, doesn't mean it's doing it correctly.
Ours wasn't cooling well on propane a few years ago so I troubleshot it to see if I could figure out what the problem was. Turned out the burner itself had rusted/corroded and was not directing the flame up the flue correctly. Installing a new burner solved the problem. Might be something to check.
03 Itasca Sunova, Workhorse P32 with the 8.1 and 4L85-E