My Sta-Rite jet pump is cycling on about every 8 minutes. 65' well, 40' of suction line. I can watch the pressure gauge at the pump go down to 35 psi and kick on til 55 and shut off. Pressure switch is working ok. I have an output shut off valve a few feet after the pressure tank shut off. I've already replaced the Sense line to pressure switch which had a leak. Replaced foot valve and Pipe cup seals by foot valve, and casing adapter seal where jet pump sits on top of 2" PVC well casing. Found shrader valve leaking on top of pressure tank, but replacing it dn help. Pulled the pressure tank and plugged hole. Now the leak real shows as pump has to kick on every 10 seconds. Acts like a leak in the casing or suction pipe in the well. No sign of any external water leaks anywhere. Could the there be an internal pump casing leak where the suction side and pressure side of the pump are equalizing? What else could it be? Thanks in advance for the help.