Just a quick one. I have a pump, it works and then stops. I change the pump with my spare, it works it stops. I then replace it back with the original, it works, it stops. I replace it with the spare it works it stops. What is going on. Do I need to buy a thrid pump or is their dark magic at work. Has anyone had similar problems, how long do pumps generally work for. To they start and stop and how can i stop this issue as I leave home all in order and arrive at a customer and then bugger me it is not working. Any advice welcome