Yes, it sounds like you have a leak. Having the pump come on by itself when no water is being used is a classic leak indication. If you don't see water spraying or dripping anywhere, it could be pump's internal valves are leaking and the water is going back into the tank just like Johndale describes.
If you have a shutoff valve between the water tank and the pump inlet, try closing it immediately after the pump first stops after a flush. Wait long enough to see if the pump still tries to cycle. If it does not, then you have found your leak: it's the pump. If it does try to cycle, open that valve right away or else the pump will be straining against the closed valve.
Does it ONLY happen while flushing? if so, it could be a leak inside the toilet. Open a sink valve long enough for the pump to start pumping, then turn it off. Does the pump stop and stay stopped? If so, the leak could be in the toilet (maybe the water valve is sticking and it's taking a few minutes for the it to close completely?) If it still does the cycling, then it's likely not the toilet and is elsewhere.
Don't let this just sit without figuring out what's going on. You could be having a leak in a hidden spot, and not notice it until it's done a lot of rot and damage.
Adam and Sue, and a pack of little furballs
2007 Holiday Rambler Endeavor 40PDQ Limited Edition - Cummins ISL 400
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