I've had this problem before with my Ralley and it sounds like you have a pressure switch in the system it's white in colour usually, and is on the cold inlet and has knurled knob on top turn it clockwise to close it. Turn on a cold tap. Turn the knob of the pressure switch anti clockwise until it starts clicking then stop allow the water to flow from the tap until it runs steady then turn off the tap it should then shut down the pump. Each time the pumps runs on you will have to adjust the switch again.
To see what a pressure switch looks like, in your search engine type in the box 'Whale leasure water pressure switch '.
Hope it helps.
Bob, April 2009
