I have a 6605 JD with 3300 hrs on it. Pto is shutting off on its on. You can pump the clutch on the tractor 2 or 3 times and the pto will start back up for a short time and quit again.. I have changed the cylonoid on the pto and that didnt help.. Any help would be greatly appreciated.. This kind of stuff happens everytime in the middle of hay season... thanks..