"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?

No. They are typically flat and generally tilt towards a low end of the tank
for all the gunk to collect at. The pump is suspended by the tank unit up
from that position. There are ridges for rigidity on some tanks but those
ridges generally run in a direction so as to drain to the low spot of the
tank and the low spot is typically the forward end facing towards the front
of the vehicle. This allows for more ground clearance under the back of the
vehicle. That area is also the most vulnerable and typically will be the
damaged/ruptured area when a driver drives over an obstacle.




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.

I would say that a pint of fuel could collect, maybe depending ont he
damaged area but if the damage is located on the front bottom it is likely
very very little will remain. Keep in mind a puntcture on the bottom of the
tank will act exactly like a can of juice. Hold the juice can and poke a
hole in it from the bottom. Juice will come out and as it comes out air
will replace the leaking juice otherwise the fluid would not drain.
Gasiline works the same way.





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.

Yeah I am sure there is a secondary back up measure there are countless
others in the fuel lines and in the old days the carburetors had
preventatice features to limit fuel flow.