the pump has pressure and vaccum valves inside, it turns off then the threshold vacuum or pressure is reached, it that value is not reached the pump will run on. if this isn't fixed soon the pump will burn up. you can verify this on a woking system by disconnecting the line and connecting a guage, the pump if working properly will turn off almost immediately. if you do not have a gauge, use your finger while actuating the lock at the trunk, or at either front door with an assistant