Naked electricals inside fuel tank?

[Fazerider]

At normal temperatures, so long as there is some liquid fuel present, the ratio of petrol vapour to air will be much too high to burn. It's a bit counter-intuitive, but very low temperatures, just above the flash point (-46ºC) are when you could potentially have an explosive mixture. Of course, you'd need the electrical bits to be arcing too to provide an ignition source.