Determining the size of a leak in a fuel tank system

An engine controller for a vehicle having an internal combustion engine, which is developed for carrying out a method for determining a size of a leak in a fuel tank system of a vehicle having an internal combustion engine, the method comprising:

• starting the internal combustion engine;
• determining a stoppage time for the vehicle, the stoppage time being a length of time the vehicle was switched off before starting;
• calculating a temperature difference between the fuel in the fuel tank system and a vehicle environment;
• checking whether at least two of a plurality of diagnostic conditions are fulfilled, wherein:
• a first diagnostic condition of the plurality of diagnostic conditions is checked, the first diagnostic condition is fulfilled when the stoppage is longer than a predetermined minimum stoppage time,
• a second diagnostic condition of the plurality of diagnostic conditions is fulfilled when the temperature difference is smaller than a predetermined maximum temperature difference, and
• when the at least two of the plurality of diagnostic conditions are fulfilled, carrying out the following steps:
• shutting off the fuel tank system,
• waiting until a predetermined waiting time has elapsed,
• evacuating the fuel tank system,
• recording a time profile of a pressure in the fuel tank system;
• and
• determining the size of a leak in the fuel tank system based on the recorded time profile of the pressure.

A method for determining a size of a leak in a fuel tank system of a vehicle having an internal combustion engine, the method comprising:

• starting the internal combustion engine;
• calculating a temperature difference between the fuel in the fuel tank system and a vehicle environment;
• and
• checking whether at least one of a plurality of diagnostic condition is fulfilled, the at least one diagnostic condition of the plurality of diagnostic conditions is fulfilled when the temperature difference is smaller than a predetermined maximum temperature difference, wherein
• when the at least one of the plurality of diagnostic conditions is fulfilled, carrying out the following steps:
• shutting off the fuel tank system,
• waiting until a predetermined waiting time has elapsed,
• evacuating the fuel tank system,
• recording a time profile of a pressure in the fuel tank system;
• and
• determining the size of a leak in the fuel tank system based on the recorded time profile of the pressure.