So what really *is* vapor lock

[Ted Borck <tborck@domain.elided>]

> 
> In a brilliant stroke of genius, Chris & Ranae Procyk <procyk19@domain.elided>
> blurted out:
> 
> >So what really *is* vapor lock?
> 
> My understanding is that the term refers to a situation where fuel turns
> from a liquid state to a gaseous state due to the application of heat.

Vapor lock is caused by a heat buildup in the fuel line between the fuel
pump and carb which causes the liquid gasoline in the gas line to exceed
its vapor pressure point and vaporize.  Fuel pumps are designed to pump
liquid and not vapor (I can't use the word gas - it would cause too much
confusion).  Furthermore a liquid is "not" compressionable (I think that
is a word) and a gas-vapor can be compressed - thus no flow to the
carb/injectors.

Trail/Road side cures for vapor lock range from pouring ice-melt (from a
moutain stream/beer cooler) water over the fuel line running from the carb
to the fuel pump - to wrapping the gas line in aluminum foil (you can
wrap some ice cubes in the aluminum foil).  

If you are suddenly a victim of vapor lock (and this has never happend
before to you), chances are the vapor lock was caused by your *last*
purchase of gasoline.

Gasoline refineries formulate automobile gas differently for summer as
opposed to winter.

If it is *real* cold outside - you want the gasoline spraying into your
intake manifold to vaporize very easily.  Thus winter gas has a very low
vapor point. 

That is *one* of the reasons methanol (which doesn't [easily] vaporize
below 60 degrees) has not replaced pump gasoline.

Conversely during hot weather - you want your fuel to not vaporize in the
fuel line but wait until it hits the pressure drop of being
sprayed/discharged into your intake manifold.  Thus summer gasoline has a
very high vapor pressure point.

You ain't going to go - unless your fuel/air reaches a stoichiometric
ratio. <g>

Vapor pressure point is one of the things the state gasoline inspector
checks for when he inspects the service station gas pumps and gasoline for
sale.

If you happend to get a tank of *winter* gas during a warm snap, or drive
out of the high mountains into a vally with summer temperatures, the heat
buildup combined with bumper to bumper traffic, and the low vapor point of
the winter gas can cause vapor lock.

It is also possible to buy old (unsold) winter gas stock being sold during
warm weather. You won't see that advertised.

If you suffer from sudden vapor lock, after you get restarted - go to a
different gas station and purchase more gasoline.

One more thing - just because it says Exxon-Shell-Amoco doesn't mean that
is what you are purchasing.  That is only the sign at the station - and
sometime(s) on the delivery truck.

The state inspectors don't check for brand of gasoline.

Hope this helps

Ted Borck	tborck@domain.elided