I think these dudes figured it out.
http://www.dtc.army.mil/publications/810f-change.pdf

The question never was will it explode if the fuel/air ratio is within a certain range it was will there be enough Oxygen inside a tank to meet this ratio. The amount of Oxygen required to cause a fire/explosion is quite different than the optimum ratio of fuel/air for running an engine which can be quite narrow but it does not take much air mixed with the vapors inside a gas tank to cause an explosion. If someone wants to believe that sparks inside a gas tank will not cause an explosion then so be it. Common sense tells us that air has to enter the tank as the fuel level drops so Oxygen WILL be present in varying ratios some of which may not support combustion but also some that will. When the temperature is really low there will be far less gas vapor in a tank than there will be on a hot day so the Oxygen/fuel ratio will be high and when the tank is warm the Oxygen will be low and there will be various ratios between. The bottom line is sparks inside a gas tank WILL be very dangerous and argue all you like to the contrary it can STILL explode!

I agree with the soldered, marine butt connectors, and covered with heat shrink method. If possible, stagger the two connections so that your repairs are not adjacent to each other.
Another minor issue is gasoline formulations. A type of insulation that is gas resistant today may not be ok with whatever they put into "gasoline" in the future.

Some insulating materials that are perfectly fine with gasoline will deteriorate rapidly when exposed to Alcohol, at least in concentrations much above 10%.

I agree with you old red. The only way possible for there not to be oxygen in the tank would be for it to be completly full. But I think you get my point about the density of the vapor. Too dense = not enough oxygen for an explosive reaction. Not dense enough = not enough catalyst to sustain an explosive reaction. The ratio of gas vapor to oxygen for an explosion inside a sealed container, where no other oxygen is immediately available, is a very narrow margin. However, I don't care how you slice it, sparks in a gas tank ain't cool. I don't care what the temperature, vapor density, or oxygen level is, I don't want sparks in there.

No doubt it will never be 100% one way or the other, sometimes it may be safe and other times not. It would seem to me that on a really cold day there would be comparatively little vapor forming in the tank as opposed to a hot day.


Also another incident where gas was ignited by a cigarette occurred to me, back when I was a kid a bunch of us had gathered on an old bridge looking at a car that had run off the edge and was lying on it's top in the creek. The driver had left the scene and no one was around so we were just standing there talking like a bunch of kids will do when one of the older boys who smoked threw a cigarette butt off the bridge, I am not sure what it hit but the car had spilled gasoline and it looked like an atomic bomb went off! First flames flared up then a few seconds later the tank went boom and that's when the huge fireball rose up and around the bridge. We ran like scared rabbits and did some sweating for the next couple of months because we just knew we were going to go to jail for burning that car and bridge! That was 44 years ago and the smoke/fire stains are still visible to this day on the old concrete pilings for that bridge, don't know if the law is still looking for whoever burned the bridge though.