A fuel vapor separator assembly including a housing having an open interior and a float disposed therein. At least one magnet is disposed on the float, and a sensor assembly which is responsive to magnetic fields is disposed externally of the housing. The sensor assembly senses the position of the float to determine whether vapor is present in the fuel vapor separator. If the sensor assembly determines that vapor is present in the fuel vapor separator, then it generates a signal, which a controller receives and activates a vapor vent valve to discharge the vapor and/or activates a fuel lift pump to pump additional fuel into the fuel vapor separator. The sensor assembly could be, for example, a Hall effect sensor or a reed-type sensor.