A method of operating a vapor recovery system that recovers vapors expelled from a vehicle during refueling at a fuel dispensing point and returns the vapors to an underground storage tank through a vapor flow path that is in fluid communication with an air to liquid regulator valve and a vapor pump. The method includes dispensing fuel into the vehicle through the fuel dispensing point, regulating an amount of vapor that is recovered through the fuel dispensing point with the air to liquid regulator valve in proportion to the fuel dispensed into the vehicle, detecting a parameter of the vapor recovery system, and maintaining a substantially constant pressure level in a first portion of the vapor return path that is disposed between the vapor pump and the air to liquid regulator valve.