Rv fresh water pumps are diaphragm pumps.......and are made to run dry without harm.
With water in fresh water tank, turn pump ON
Then open each faucet cold side then hot side to expel the air in lines.
Pump can not build up pressure to shut off with air in system.....they pump water pretty good but can't pump air worth a hoot.
Hot side will take longer than cold side because you have to fill water heater tank first before water can flow thru hot side.
If you don't get any sputtering of air at faucets....then check suction side of water pump for any loose/cracked fittings anything that may be sucking air.
The pumps are self priming IF the suction side doesn't have 'air' leak issues.
