If there is no leaking of water into the bilges, the pump should shut off. If it fails to do so, it is usually one of the non-return valves in the pump itself and water is just going in and out of the pump at high pressure--usually about 50 psi
I stripped and cleaned mine. There are two types of shut off--one is electronic and uses a piezo device to operate the shut-off, the other uses a micro-switch attached to a spring-supported diaphragm
. The piezo type operate fine without an accumulator--the micro-switch types prefer to have one. Both are adjustable.
When you get it apart, clean the pump insides etc, check the bearings and valves for damage. They are not great quality. I replaced mine when they jammed solid--but they were noisy long before that. They just get louder as they wear. When I changed them, the pump just purred. I bought Japanese stainless steel
pre-packed long-life bearings fully sealed. Why they did not use such bearings at the outset beats me. They cost me twenty five dollars as opposed to about four dollars fifty--I suppose that is the answer. The pump went on top last years--and I still have it because I switched the vessel to marina supply. The pumps are good quality--just the bearings were nothing great.