The biggest problem I have with pump gas is percolation. If I drive any car we own with straight Oregon pump swill it will boil out of the carb once the car sits and heat soaks. Non-ethanol makes no difference. Blocking off the heat riser helps some, but the problem still exists. If I fill any of these cars with a 25% 110 octane race fuel mix the problem goes away. I figured this out because my high compression race gas only car will always start right up no matter how hot it gets (within reason).

Also if the float is too low the fuel may have a tendency to percolate.

This may not be your issue but I have been fighting it ever since I moved out West.