Edit: I didn't read your second reply so what I posted is not applicable other than it should work with the hard start capacitor.
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I have a pair of 2000is and a PI voltage unit. I had the same issue initially with my 15k AC. I installed a $10 hard start capacitor in the AC and everything works fine.
I also found that if I first put a load on the generators, like a microwave or water heater, the AC would start and run just fine. It seems to be related to initial high current applications.
This capacitor should work for you.
http://www.amazon.com/gp/product/B000LDPI26?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00