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On 3 Sep 2006 at 23:38, Steven Ayres wrote:
> JimA=> There would be no tendency for fuel to move backwards
> => (toward the tank) because there are already 2 valves, in series,
> => in the pump which prevent flow in this direction.
>
> As I understand it, this feature was not in the early pumps, and the
> fuel-line antisiphon valve was used first. That proved problematic, and
> VW added the feature to the pump itself. This was talked over
> extensively some years ago on the 34 list, which has more early
> ('62-'65) cars. I've never owned a fuel-line valve car, so I have no
> direct experience to confirm anything.
All pumps have the 2 series check valves; that's just a necessary
part of being a pump, but I suspect that the little extra device did
come somewhat later, after VW started getting feedback on the
problem. The valve built into the pump came even later once it became
obvious that solution #1 wasn't working as well as hoped. (It was
probably more expensive, too, if only because it required someone to
install it separately at the factory.)
> We were talking about losing fuel from the carbs before: where do you
> think the fuel would go?
I expect a certain amount of it to boil off in the heat soak after
shutdown. After that, a certain amount evaporates every day. The big
question amounts to, "How much fuel just boils away after I shut down
a hot engine?"
I think you already pointed out that there's no way for fuel in the
float bowl to get sucked back up into the line, and on that we agree.
--
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Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
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