I've been curious about this for a long time. I realize that they have been submerging fuel pumps inside of fuel tanks for many years, and I can not remember hearing about an explosion.

Seems to me that a spark from the wiring would turn the entire fuel tank into a fireball. Why does this not happen?

 

If you open a conventional fuel pump, theyre actually open inside with the armature, commutator, and brushes exposed, which is the real reason you need to change your fuel filter every so often. The inside of the motor is exposed so fuel can flow through and cool it. Otherwise, it would overheat and burn out.

The reason they dont ignite is that, under virtually almost all conditions, the fuel mixture in the tank is FAR in excess of whats needed to ignite as gas vaporizes readily and displaces almost all the oxygen.

Its possible that if you left the tank near bone dry and came back after a few months and forgot about it, you could have an explosion, but Ive never heard of it hapening.

 

Like Dimented said, it basically boils down to "no oxygen". Gotta have fuel, spark and oxygen to have combustion. Take any one of the three away and it won't happen.

 

Plus a spark inside the fuel won't ignite because of the lack of oxygen. Only the vapors are explosive but again, they need the proper oxygen mixture before ignition will occur.