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RE: [T3] As the Tank Turns - this weekend's episode

On 10 May 2006 at 5:50, Big Al wrote:

> My 70 does not have an overflow tank or charcoal
> tank though.  It/they might have been removed, I haven't made it a
> point to look for the canister.  The hose from the vent on the left
> side of the tank went down the wiring hole under the brake fluid
> reserve and stopped.  that's it.

If your '70 was originally sold in the US then it came with the overflow tank 
and charcoal cannister. You might be able to find the remains of the overflow 
tank bracket under the LF fender, and the '70 charcoal cannister was mounted 
under the deck to the left of the engine. It was VERY much in the way there, so 
it got moved to above the transmission the next year.

> The 71 tank had the same setup, so this may have been the common "fix"
> to a suspected failing charcoal system?

Yes, or for the '70 models, I suspect some of them were removed even earlier 
just because they were so much in the way.

> > I'm sure that there's still enough clearance for gravity flow, but with the FI
> > systems, the return flow drags along extra gas so that the central cup will get
> > filled to a level higher than the rest of the tank. You can actually observe
> > this when you start up the car with a low tank. You may have noticed that a
> > block or 2 later the gas tank doesn't look nearly as empty as when you first
> > started up. This is because the center cup, where the gauge is, is now more
> > full than it was when you first started the engine.
> Wow...  this reinforces that the VW gas guage reading is questionable at
> best.  ;)  :D

Yes, and if you watch the tank with the pump running and the sender removed, 
you can see the gas in the cup rise as much as 4-6" above the main tank. It 
explains why the "bottom half" of the tank doesn't seem to last nearly as long 
as the top.

In fact, this might be a good test of your misaligned holes, if you were 
willing to try it before drilling. If the "jet pump" works, and fills the cup 
higher than the main tank, then I'd just leave it alone. I'd be interested in 
how this turns out.

Jim Adney
Madison, WI 53711-3054

List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org

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