Although the in tank fuel pump of a vehicle sits in gasoline and creates small sparks it is safe in the gasoline tank and cannot catch the gasoline on fire due to a lack of oxygen and air in the tank.
Although there might be a slight amount of oxygen and air introduced into the gas tank there's not enough of it to cause the fuel to ignite simply from the spark.
For the gasoline to catch fire or explode you need more than a spark and you need oxygen, air and the fumes for it to get the gasoline to explode.
That's why you need air to come into the engine to cause the explosion of gasoline into the cylinder.
You could place a lit cigarette or even a lit match into a bucket of gasoline and it won't ignite or explode because it takes more than that to cause a fire or explosion with the gasoline.
The cigarette or match will just go out.