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

I will agree it _is_ something of a mental twist that the very volatility
of gasoline is in fact the property that mitigates the fire hazard
suppressant from the fuel pump when the tank is low (although I presume
the pumps are mounted in a well or at least at the lowest point in the
tanks in order to keep them submerged until absolutely all fuel that can
be picked up has been. I suppose one could even raise the inlet pipe a
little to ensure that; don't know if they do or not.)

hth....

-dpb


While the explanation is valid and works for 99.999% of the time my question
is about the other .0001 percent of the time. When the lost gas cap is
never replaced and the car is parked and sits for several months with little
fuel. Eventually some one cranks it up and the tank has little fuel to
submerge the pump.
And if you think that is not common, repositions of abandoned cars filled
the bill at the dealerships and many were often stripped.

While perhaps it is relatively common, it's still highly unlikely to be
a problem. If there's enough fuel to crank and start the engine,
there's enough to suppress the spark and have high enough vapor pressure
to prevent flammability at any temperature above about -10F. Remember
the flashpoint of gasoline is -40C (which iirc is the magic point where
-40C=-40F???).

About the only time above about 0F one could get a real problem would be
an essentially dry tank w/ residual vapor and run the pump dry. I'd
think that if vehicles were so poor condition as to be left w/ empty
tanks and no lid there would be little likelihood of them being cranked
in any near-term time frame. Hence the evaporation over a period of
time would likely imo serve to remove even the vapors.

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