[T3] Update with a Bowl Full of Rust Flakes

[Jim Adney]

On 23 Jul 2011 at 22:15, SCS Crewcab wrote:

> Boy, this sounds ** really ** complicated!  When I look into that cup 
> from the opening for the fuel sender, I see a direct opening to the 
> return line going out of the tank. Looking from the bottom up through 
> that return line, I don't see any openings in the the line other than 
> the one that opens directly into the cup.  Do I have some kind of 
> aftermarket tank?

Sounds like the standard tank, you just can't see that detail from 
above or below. If there were no other opening, it's pretty clear 
that this would run "out of gas" once the tank dropped to something 
below about half a tank.

If you watch in the tank with the engine running and the tank quite 
low, you can see that the cup will be full, and actually spilling 
over, while the level outside the tank is well below that in the cup. 
You can also see a high area above the return port, from the momentum 
of the returning gas. 

There's no easy way that I know of to actually see the passages that 
are involved, but you can see the effects of the system on the gas 
level. It's interesting, for example, to watch what happens when you 
start the engine, or just start the pump, with the tank level low. 
You can watch the cup fill up and then overflow.

Somewhere over the years I've seen a published sketch from VW that 
shows this scheme, and Dave Hall has a sketch of his own on his web 
site that shows how it works. Dave usually steps in and gives us the 
link to that page whenever this topic comes up.

-- 
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
*******************************