Chang 'an Star seems to fart when it refuels.

That's because the mixture is too strong. The mixture is too rich to burn completely in the cylinder, and then it may pass through the exhaust pipe and burn in the exhaust pipe, so there will be ignition. This is related to oxygen sensor, intake pressure sensor and so on. It may also be caused by the dirty throttle. There are many reasons that need to be checked in order to make the most accurate judgment and maintenance. It is recommended to go to the repair shop to find a master to check and do the most reasonable maintenance. I hope I can help you and be adopted.