[rotorwrench]

I don't know whether the car has an original type zenith or a later aftermarket Tillotson carb. Both are updraft types and both have an adjustable main mixture control or GAV that is controlled by turning the choke rod. Both carbs work the same way but are a bit different on how they function so it's nice to know what you have.

Pulling the choke will enrichen the mixture but excessive cranking with it pulled will flood the carb and it will leak out onto the floor or ground below. A float valve that is stuck open will also flood the carb and come out the bowl vent.

Model A gas tanks are all old and in varying states of condition. If fine particles of rust get past the filter bowl then the carb can get crud in the float bowl that will eventually make it into the fuel delivery circuits and can plug them up. They can also get plugged with varnish from old fuel if they set too long. If the car won't idle on its own then either it's not getting enough fuel supply from the tank or the idle circuit is plugged or maladjusted. Adjustment of the idle mixture depends on the carb you have on there.