Shut of the fan let the pump run, if it does not stop at all, then first thing, check your checkvalve which comes from the T then goes to the engine , blow in one end, and suck on it if you can blow in both ends it is bad, just trye to loosen it inside with a needle, if this does not work then buy the napa, check valve $5.50 2-1015 make sure the side which allows air thrue goes to the pump side.