besides the possibility of vapor lock, there's also another factor to
consider... - the length of fuel line from the fuel pump to the engine. On
2WD it's quite long and the fuel pump must work harder and the fact in hot
temp. the fuel line expands thus the fuel pressure will drop.
I made an offroad North/South trip on the Saline Valley trail (Death
Valley) it's quite high temp at noon when were half way (about 110°F) on a
tintop Syncro. It was so hot that when we stop for a rest I can hear the
gas boiling in the tank making gurgling noise. But we never has the vapor
lock or stalling problem. I suppose since the gas tank on Syncro is in the
rear, the length of the the hose from the gas tank to the engine is quite
short and that helps, the fuel pump is a Bosch.
Then we need to look at the pressure spec. and delivery gas volume of the
fuel pumps to compare. I guess the Bosch, Delhpi, Pierburg all have
different delivery pressure and gas volume.

On Thu, Jun 20, 2019 at 1:05 PM Ryan Cresawn <jrcresawn@gmail.com> wrote:

> Mark,
>
> I agree with your diagnosis of vapor lock. A few people in Arizona with
> air-cooled Buses have told me the same thing.
>
> Ryan
>