Lyle
I think Steve is right the fuel line coming from the fuel tank may be cracked and sucking air or it could be sucking air at the fuel filter.
Either way the aquahot is temperamental with fuel delivery it needs clean fuel no bubbles or it will be intermittent and flame out.
Try running the unit with the feed pickup line running out of a five gallon fuel can of diesel this will check off fuel delivery as the problem.
Remember the unit will be returning fuel back to the coaches fuel tank so make sure you have room in the tank to take the extra fuel .
Hope this helps
Eric