System and method for testing for error conditions in a fuel vapor recovery system

A fuel delivery and vapor recovery system having error detection capabilities incorporated therein for detecting blockages, comprising:

• (a) a nozzle connected to a fuel source;
• (b) a vapor transfer line connected to the nozzle and leading therefrom to a vapor reservoir, the vapor transfer line including an inlet line and an outlet line;
• (c) a vapor pump connected between the inlet line and the outlet line of the vapor transfer line;
• (d) a first test valve connected in the inlet line of the vapor transfer line;
• (e) a second test valve connected in the outlet line of the vapor transfer line;
• (f) first and second actuators for opening and closing the first and second test valves independently of one another such that sections of a vapor transfer line between the respective test valves and pump can be isolated;
• (g) a processor and pump controller for controlling the pump speed to generate pressure in either of the isolated sections of the vapor transfer line;
• (h) a first pressure sensor connected in the inlet line for sensing the pressure in the isolated section of the inlet line and producing a test pressure signal corresponding to the sensed pressure;
• (i) a second pressure sensor connected in the outlet line for sensing the pressure in the isolated section of the outlet line and producing a test pressure signal corresponding to the sensed pressure;
• and
• (j) said processor and pump controller having a test mode and being connected to the actuators to cause the actuators to open and close the first and second valves during said test mode, said processor and pump controller operating the pump and receiving test pressure signals from at least one of said pressure sensor during said test mode and processing the pressure signals to derive the restriction in the vapor transfer line and comparing the derived restriction with a standard reference to determine if a blockage exists in the vapor transfer line.

A vapor recovery fuel dispenser comprising

• a. a liquid dispensing nozzle and a liquid conveying line to said nozzle,
• b. a vapor return port in said nozzle connected through a vapor return line to a vapor reservoir,
• c. a valve in said vapor return line between said nozzle and said reservoir,
• d. a pump in said vapor return line between said valve and said reservoir and driven by a motor for pumping vapor through said vapor return line at a volumetric rate determined by the pump motor speed, said motor and pump being arranged so that when the motor drives the pump at a given speed with said valve closed, a repeatable vacuum is normally generated in said vapor flow line,
• e. a pressure sensor in said vapor flow line between said valve and said pump outputting a pressure signal representative of the vacuum in said vapor flow line between said valve and said pump, and
• f. a controller operatively connected to said motor, said valve and said sensor and
• i. adapted to normally operate said motor at a desired speed to pump a desired amount of vapor through said pump and
• ii. adapted to from time to time operate in a test mode in which the controller
• (a) closes said valve,
• (b) operates said motor at a predetermined speed and
• (c) compares the vacuum sensed by said pressure sensor with a stored value to determine any needed re-computation of the relationship of the motor speed to the volumetric flow through said pump to assure control of the volumetric flow.