"One thing to keep in mind is that as the engine is running fuel is
recirculating throught eh system, picking up heat from the engine and
from the pumping process eventually raising the temperature of the fuel
in the tank.  As the temperature increases so does the vapor pressure
making vapor lock that much easier to occur. If the fuel vaporizes at
the suction inlet of the pump all bets are off."

Ah. Dennis, that might be it. The periodicity of the shut-downs
correlated with the heat and grade. The steeper and hotter, the more
frequent, at one point giving a 15 second on / 5 second off duty cycle,
and maybe a pump creating cavitation bubbles would do that.

If that's what it is, then there's no solution except pull over to the
side of the road -- if the mountain road in question has a shoulder --
and let things cool. While sitting in 100 degree F conditions and, as
these things usually work out, in direct sunlight, too.

(Grasps at straw) Maybe removing the pre-pump filter would cut down on
the cavitation.

--
Jack "Rocket j Squirrel" Elliott
1984 Westfalia, auto trans,
Bend, Ore.

On 08/19/2012 07:26 PM, Dennis Haynes wrote:
> Almost all modern fuel injected vehicles have the filter on the pressure
> side, (after), of the pump(s). Not only did VW make this change starting
> with the 2.1 they also enlarged the fuel tank outlet.
>
> One thing to keep in mind is that as the engine is running fuel is
> recirculating throught eh system, picking up heat from the engine and from
> the pumping process eventually raising the temperature of the fuel in the
> tank.  As the temperature increases so does the vapor pressure making vapor
> lock that much easier to occur. If the fuel vaporizes at the suction inlet
> of the pump all bets are off.
>
> My first motorhome (1992 Ford E350 chassis) had this problem with the pump
> even installed in the tank. At one point down in Florida I got stuck with
> it.  After being towed to a dealer the tow truck driver told me that this is
> a common problem and in a few hours it will run again. Ford's fix with a
> redesigned pump which also required a new mount, gauge sensor, and some
> other stuff. Some $900 later plus a rental car etc. All that on a vehicle
> with less than 40,000 miles on it.  FWIW my 88 Fox has two pumps, a transfer
> pump in the tank and the main pressure pump. Common on many VW products.
>
> Dennis