Leak detection a vapor handling system

A method of leak detection in a closed vapor handling system of an automotive vehicle while an engine is running comprising:

• providing differential tank pressure sensor that provides pressure;
• closing a canister purge control valve to seal the system from the engine and an atmosphere;
• waiting for a first period of time;
• closing a shut off valve;
• waiting for a second period of time;
• determining a pressure sensor offset;
• estimating a correction value for vapor generation;
• aborting the leak detection if the correction value is greater than a control correction value;
• calculating a pressure mean value;
• dropping the pressure to a first threshold pressure by opening the control valve for a third period of time;
• detecting a tank cap missing condition if a second threshold pressure is not reached within the third period of time;
• detecting a large leak condition if the pressure drops between the second threshold pressure and the first threshold pressure within the third period of time;
• aborting the leak detection if the speed of the automotive vehicle is greater than zero;
• ending the leak detection if a fuel volume is not within a control volume range;
• evaluating a pressure slope over a fourth period of time;
• calculating a corrected pressure slope using the correction value for vapor generation;
• and
• determining a leak diameter by comparing the corrected pressure slope to pressure control values within threshold times.

An automotive evaporative leak detection system comprising:

• a pressure sensing element;
• a control valve;
• a shut off valve;
• a processor operatively coupled to the pressure sensing element, the control valve, and the shut off valve and receiving pressure signals from the pressure sensing element and sending signals to the control valve and the shut off valve;
• wherein the processor closes the control valve and the shut off valve, generates a vacuum, analyzes the pressure signal at threshold times, compares the pressure signal to pressure control values, and determines a source of leak condition from a plurality of source of leak conditions;
• wherein the plurality of source of leak conditions include a tank cap missing condition, a large leak condition, and a leak diameter.

An automotive evaporative leak detection system comprising:

• a differential tank pressure sensor located on a conduit between a fuel tank and a canister, the canister communicating with an engine and an atmosphere, the fuel tank communicating with the engine;
• a shut off valve located between the canister and the atmosphere;
• a control valve located between the canister and the engine;
• and
• a processor operatively coupled to the differential tank pressure sensor and the shut off valve and receiving pressure signals from the differential tank pressure sensor and sending signals to the control valve and the shut off valve;
• wherein the processor closes the control valve, waits for a period of time, closes a shut off valve, determines a pressure sensor offset, estimates a correction value for vapor generation, calculates a pressure mean value, drops the pressure to a threshold pressure, detects a tank cap missing condition, detects a large leak condition, aborts the diagnosis, evaluates a pressure slope, calculates a corrected pressure slope, and determines a leak diameter by comparing the corrected pressure slope to pressure control values within threshold times.