Did you get to the bottom of why this unit is hard to start. we have one that seems to have the same problem Tier 4 engine. Extremely hard to start , but when it does it runs absolutely fine. once you shut the engine off and let sit even for 10 seconds its back to a very long hard start. its acting like a check valve of some sort is not holding back pressure on the system. I'm trying to get some service info on this unit.