Not sure if this will help you but a while back local deere mechanic was working on something else and got to talking. We have a 320d and he suggested changing a fuel check valve on ours for preventive maintenance. It was on back of motor and had to raise cab to do it. He never said why that I remember but worth checking out. We were having no issues so not sure if this is what he was trying to prevent but he did say something about hard starting now that I remember more. Has been a year or two.