have the same problem with mine too. Dont really have a water seperator, it has a screen with plastic bowl under tank, but not similar to the 9600 element/bowl seperator. Ive changed all the check valves on mine too using the dealer and still same problem within three days time it wont start. My 8420 has the same engine with same filters and check valves and it has never given me any problems so Im thinking its not related to those parts but something else. Maybe on the return circuit? I dont know but Im not happy with the issue and have been fighting it for a couple years now.