If yours is like mine , its a bellows type pump & since it did work for a couple of tanks of water , I would look for obstructions in the suction line or strainer .They can fail as with anything else , but normally have a good service life & they don't need a head of water to prime them , meaning they don't need to be below the water line to pull a suction to prime . Crack, break or loose fitting in a suction line pulling in air , can keep them from priming . A bad or hole in the Diaphragm of the Pump can also keep them from priming .
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