"dpb" wrote in message
...
Leon wrote:
...

If there is a hole in the bottom of the tank, it is absolutley below the
pick up level. ...

But are the pumps mounted in a well? Are there not formed hollows/ridges
for structural rigidity in the tanks? Even if it leaks to the point of
not running, I'd expect there to be a little gas in almost all cases left
in such areas. If the tanks were a perfect sphere and you punched a hole
at the very bottom, all the liquid would run out, yes. But there still
wouldn't be air intrusion in most cases, only almost pure vapor.


Added to that that the brushes are undoubtedly built to be non-arcing so
that there really isn't a continuous ignition source, the conditions
just aren't satisfied.

That may be the case. Non arcing brushes and again the brushes were in a
strongly built contained steel enclosure behind a steel ball check ball.

So, there's the design feature(s) you're after which are simply part of
the design. I'm not saying the pumps are built w/ no thought of
preventing an ignition source; only that I'm convinced there's no
secondary protective device or system other than the base design and the
physics of gasoline combustibility.

--


It may also be that even when the fuel/air ratio conditions for combustion
are met, the arcing from the brushes may not provide a high enough
temperature to instigate ignition. (The article in the url below gives an
ignition temperature of 600F for gasoline vapor.)

http://tinyurl.com/yanzowk