failsafe switch for shallow well pump

Here is the deal...I use a shallow well pump with a 30-50 switch that is used in a very old carwash. The pump is used to pressurize my tire cleaner chemical to the system. My problem is that i have gone through about 4 pumps in the past year. What happens is that if there is a leak in the line, the pump turns on as it should to try build pressure. Well..when there is a leak in the hose or on the pressure side of the pump the pump runs non stop ot try to reach the turnoff pressure. By doing this..it not only wastes all my chemical...it also ruins the pumps because it never shuts off.. What i was wondering is if there is some sort of turn off switch or fusable link i could use...so when the pump runs for over 1 min at any given time obviousy there is a leak in the systems and therefore should shut down...not only to save chemical but also the pump itself....This is getitng expensive..there has to be some sort of easy fix to prevent the pump runing not stop in such a situation...PLEASE HELP...im going broke here...

George B