I don't think that humidity has much to do with it except to the extent that it
affects
air density and therefore (possibly?) air pressure. I'm not certain how
significant that
effect might be. A combination of sufficiently high temperature and low ambient
pressure
will allow fuel to form vapor bubbles; the fuel is actually boiling, and since
the fuel
system is designed to move liquid fuel, not vapor, the engine is starved of
fuel. This is
why the "slurpee fix" is effective - cooling the pump returns the fuel to the
liquid
state. The trick of running the fuel line in front of the radiator is after the
same
effect - keeping the fuel cool. Winter fuel formulas can have a lower vapor
pressure than
summer formulations because of the lower ambient temperatures in the winter
months -
boiling point is determined by both pressure and temperature, so given the same
atmospheric pressure conditions but lower temperatures a more volatile fuel
will still be
acceptable.
I may have missed some nuances of the phenomenon, but I'm pretty sure I hit the
essentials... (It's been a while since Chem 1A).
Gary McCormick
San Jose, CA
CalSpeed@aol.com wrote:
> In a message dated 31-08-99 9:19:08 AM EST, chubbard@shl.com writes:
>
> << Here in the hot
> part of the USA, vapor locks cause the same symptoms. After stopping for a
> slurpy, the car ran like it was out of gas. Dumped that crap on the pump and
> waited a minute. It fired right up. This still happens on occasion. I'm too
> cheap to buy a new pump. >>
>
> Hello,
>
> Is there a way to prevent vapor lock? Would a new fuel pump correct that
> prevent phenomenon from happening? Btw... what is vapor lock? I have an
> idea that it has to do with extreme temperature changes and ... humidity?
>
> Michael "Calspeed" Carion
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