Sounds like a lift pump or pre lift pump issue such as low fuel, sucking air from tank hose or connection or the impeller shaft on the LP sheared. The simplest way to find out if it is tank or supply line issue is to get 5 feet of 5/16 fuel line and slip it over the LP fitting with the other end in a 5 gallon can of diesel. You will have to reprime the system to suck the fuel thru the pump. Prime the same as you would with a filter change. So far it is not the VP44.
Dave