Thanks Ray. I'm looking for a basic how duel fuel systems work. The old Briggs & Stratton small engine service manuals would include a description and simple diagrams to show a 2 or 4 cycle engine works. The Duel fuel systems have a switch that you switch between propane and gasoline, even when running. On the bottom of the carb there is solenoid which probably cuts the gasoline off when you throw the switch to propane. I cant figure out where the propane would enter the fuel system, maybe a jet on the intake manifold or a secondary jet in the carb? With me generators seem to follow Murphys law and don't start during blackouts and storms. Perhaps if I find a diagram of a combustion engine that runs on propane only I can combine the principals with the gasoline engine. I cannot find any repair manual for Cummins and Onan only owners manuals.
