Test probably wasn’t the right meaning. I didn’t mean to test it once, but to exercise it regularly to ensure everything is working. Stationary units often self-test weekly. I try to test my diesel unit monthly, but sometimes I’ve gone a little longer than that.

The gas tank provides a gravitational feed to the carb.

The carb has a bowl.

The bowl is closed by a float valve.

When the float valve fails, the tank continues to empty.