1. If discharge tubing is installed the bleed valve is closed and needs to be opened during priming. Note: Not all pumps have bleed valves.
2. There may be an air leak on the suction side. The liquid end may be missing an O-ring on the suction connector or the valve may be loose.
3. The foot valve may be clogged and may not be allowing fluid to pass.
4. The pump stroke length control may not be adjusted properly.
5. Dried chemical may have accumulated in the liquid end, preventing the valve ball and seat from checking properly.