Method for conducting a leak test of a tank ventilation system of a vehicle

A method for checking the tightness of a tank-venting system of a vehicle, the method comprising the steps of:

• introducing an overpressure or underpressure compared to the atmospheric pressure utilizing a pressure source alternately into the tank-venting system and a reference leak of a defined size connected in parallel to the tank-venting system over a pregiven time interval;
• detecting at least one operating characteristic variable of the pressure source when introducing the pressure into the tank-venting system (tank measurement) as well as when introducing the pressure into the reference leak (reference measurement);
• comparing the two measurements;
• drawing a conclusion as to a leak when there is a deviation of the tank measurement from the reference measurement by a pregivable value;
• drawing a conclusion as to the operability of the tank-venting valve of the tank-venting system from the time-dependent trace of the operating characteristic variable for the tank measurement;
• after ending the tank measurement, opening the tank-venting valve and detecting the time-dependent trace of the operating characteristic variable;
• and,
• drawing a conclusion as to the operability of the tank-venting valve when the operating characteristic variable drops by a pregiven value within a pregiven time.

A method for checking the tightness of a tank-venting system of a vehicle, the method comprising the steps of:

• introducing an overpressure or underpressure compared to the atmospheric pressure utilizing a pressure source alternately into the tank-venting system and a reference leak of a defined size connected in parallel to the tank-venting system over a pregiven time interval;
• detecting at least one operating characteristic variable of the pressure source when introducing the pressure into the tank-venting system (tank measurement) as well as when introducing the pressure into the reference leak (reference measurement);
• comparing the two measurements;
• drawing a conclusion as to a leak when there is a deviation of the tank measurement from the reference measurement by a pregivable value;
• drawing a conclusion as to the operability of the tank-venting valve of the tank-venting system from the time-dependent trace of the operating characteristic variable for the tank measurement;
• detecting the time-dependent trace of the operating characteristic variable during a tank measurement carried out during idle of an internal combustion engine (idle measurement);
• detecting the time-dependent trace of the operating characteristic variable in a tank measurement executed for a switched off internal combustion engine of the motor vehicle (run-on measurement);
• and,
• drawing a conclusion as to a disturbance of the tank-venting valve when the time-dependent gradient of the operating characteristic variable during the idle measurement deviates from the comparable time-dependent gradient of the operating characteristic variable during the run-on measurement by a pregiven value.

A method for checking the tightness of a tank-venting system of a vehicle, the method comprising the steps of:

• introducing an overpressure or an underpressure compared to the atmospheric pressure utilizing a pressure source into the tank-venting system;
• detecting at least one operating characteristic variable of the pressure source when introducing the pressure into the tank-venting system (tank measurement);
• comparing the measured operating characteristic variable to a threshold, which is derived from operating variables of the control of an engine of the vehicle or is fixedly pregiven;
• drawing a first conclusion as to the presence of a leak in said tank-venting system when there is a deviation of the tank measurement from the threshold by a pregiven value;
• and,
• drawing a second conclusion during tank measurement as to the operability of the tank-venting valve of the tank-venting system from the time-dependent trace of the operating characteristic variable detected during the tank measurement.

A method for checking the tightness of a tank-venting system of a vehicle, the method comprising the steps of:

• introducing an overpressure or an underpressure compared to the atmospheric pressure utilizing a pressure source into the tank-venting system;
• detecting at least one operating characteristic variable of the pressure source when introducing the pressure into the tank-venting system (tank measurement);
• comparing the measured operating characteristic variable to a threshold, which is derived from operating variables of the control of an engine of the vehicle or is fixedly pregiven;
• drawing a conclusion as to the presence of a leak when there is a deviation of the tank measurement from the threshold by a pregiven value;
• drawing a conclusion as to the operability of the tank-venting valve of the tank-venting system from the time-dependent trace of the operating characteristic variable during the tank measurement;
• after ending the tank measurement, opening the tank-venting valve and detecting the time-dependent trace of the operating characteristic variable;
• and,
• drawing a conclusion as to the operability of the tank-venting valve when the operating characteristic variable drops by a pregiven value within a pregiven time.

A method for checking the tightness of a tank-venting system of a vehicle, the method comprising the steps of:

• introducing an overpressure or an underpressure compared to the atmospheric pressure utilizing a pressure source into the tank-venting system;
• detecting at least one operating characteristic variable of the pressure source when introducing the pressure into the tank-venting system (tank measurement);
• comparing the measured operating characteristic variable to a threshold, which is derived from operating variables of the control of an engine of the vehicle or is fixedly pregiven;
• drawing a conclusion as to the presence of a leak when there is a deviation of the tank measurement from the threshold by a pregiven value;
• drawing a conclusion as to the operability of the tank-venting valve of the tank-venting system from the time-dependent trace of the operating characteristic variable during the tank measurement;
• detecting the time-dependent trace of the operating characteristic variable during a tank measurement carried out during idle of an internal combustion engine (idle measurement);
• detecting the time-dependent trace of the operating characteristic variable in a tank measurement executed for a switched off internal combustion engine of the motor vehicle (run-on measurement);
• and,
• drawing a conclusion as to a disturbance of the tank-venting valve when the time-dependent gradient of the operating characteristic variable during the idle measurement deviates from the comparable time-dependent gradient of the operating characteristic variable during the run-on measurement by a pregiven value.