Understanding why the pump runs is one thing. The pump has a pressure sensing item built in and it is adjustable to get different pressure but it should pump to the adjusted pressure and then shut off until the the line pressure drops.
So what folks are suggesting is that there is a leak at some point where that pressure is leaking out!
It can be the check valve at the fill port but it also can be at some spot underneath where there is a leak you've not spotted yet so I would suggest looking really carefully before it keeps getting thing like the floor wet until there is need for a major repair!
If you screw a solid plug into the fill port and it still keeps cycling, then a leak is almost certain. Something like this is one option if you are not able to find one near you.
https://www.amazon.com/Camco-22103-R...ag=googhydr-20
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Richard
Why no RV year, make and floorplan on MY signature as we suggest for others?
I currently DO NOT have one!