What is the purpose of the purge valve in this system? I could only find it on Airflow's price list, without any mention of it's use. I do not have one on my Cub and have no troubles. Granted the Precision systems on Lycomings do make air in the fuel injector lines on a hot engine on a hot day when the engine is shut down. This is not a problem. Sometimes in hot weather while on the ground the engine does get air bound and can shut down. This situation is alleviated by turning on the fuel boost pump. This is also more of a problem with low wing airplanes.
My Cub has an IO-360 and it always starts easily hot or cold. Do you have electronic ignition?My Pitts has an IO-360 with Bendix fuel injection and after flying it for a long time, I wouldn't even think of putting fuel injection on a Cub.
Cold starting is pretty easy and I know how to hot start it after a 10-15 minute heat soak. After an hour heat soak, I don't have enough fingers and toes to cross.
On something that doesn't fly upside down, give me a carb any day. One gas line, a little gravity and you're off and running.