I have about a 10 year old pump with an expansion tank in my water system. Last night i tried to do dishes and when i tried to run the faucet it would only pump a good stream of water for about 4 seconds. After i would shut the faucet off for about a min. it would build up pressure for about the same 4 sec. I checked the pump and it was running but would not shut off like it would before. I just filled the tank so i know i have water in the system. I was wondering if it might be a bad pump or if the expansion tank would have anything to do with the problem, or maybe something else i might be missing. It worked fine this weekend. Any suggestions would be greatly appreciated