1. Due to too small internal pressure，It is easy to cause the fuel tank deformation，If it is severely deformed，May not even add oil，lead to unable to refuel;

2. Due to the fuel tank and outside，The oil pump will be pumped all the time，Over time, it may cause damage to the oil pump。

The sound of breath usually appears in summer，Because seabet iothe temperature in summer is relatively high，Related will occur after gasoline is heated，Because the vehicle space is fixed，Oil and gas including sealing will cause pressure，The pressure inside is greater than the air pressure outside，So there will be sound appearing when turning on the fuel tank。Actually，The sound appeared at this time，The problem is not big。

If you hear the sound of the gasoline cover，Explain the problem of carbon can or solenoid valves，The pressure in the fuel tank should be less than the pressure outside，It may cause the following two situations:

1、When the pressure in the fuel tank is less than the pressure outside，and the outside is not ventilated，Then the oil pump will continue to pump out，Over time, the oil pump may be damaged;

2、If the internal pressure of the long -term fuel tank is less than the external pressure，The fuel tank may deform，serious ones may not even add gasoline。

Summary:The inside of the fuel tank must be positive pressure，It is impossible and not allowed to generate excessive negative pressure。When I heard the sound of inhalation，Old drivers must pay attention to。