Had same problem with mine last week,
Perfect one day , not the next a smell of deisel had me thinking a leak, but no leak .
had somebody take a look ,and the inside chamber was soaked with deisel, it had not been igniting , a good clean out , some fire cement in the bottom to repair and instand heat ,although it was half an hour burning the eccess fule out of the system.
Geoff.
Mike the noise he may be hearing could be the fan on the inverter, I thought the same untill it was taken out of van, the fan does not work unless the water is flowing.
geoff