I have been on the hunt for why my 6.5NHMFA26115C Onan genset will not start unless I hand close off the intake air. I have had this problem since I ran the propane tank empty. I have had the original LPG regulator replaced, with no change in starting. I have today learned that Onan uses a special RED spring in the LPG regulator(model J). There is at least 4 springs for the model J, standard, blue, orange, and red. I am now waiting for the RK-J-2 repair kit and the new S2-136 RED spring. I hope this fixes the problems. I got this help from Carb & Turbo Systems Alternative Fuel Systems Shakopee, MN | Carburetion & Turbo Systems (http://carbturbo.com/)