[T3] Fuel Filter for 72 FI System

[Dennis Stiefel]

On 13 Sep 2012 at 20:15, Dennis Stiefel wrote:

> what kind of fuel filter do you use to replace the one under the gas 
> tank on these systems?

The OE part was made by Bosch. It was a grey plastic box about 2" x 2" x 3"
with ~5/16 nipple on each end. Aftermarket copies are commonly available
made of white plastic, but you should not use the little clear plastic
prefilters that are commonly used with carbs, because those won't handle the
flow. (The FI pump puts MUCH more gas thru the filter than the engine
actually uses, Most of it just circulates around the fuel ring and returns
to the gas tank.)

Here's a picture of a perfectly good aftermarket one:

http://www2.cip1.com/ProductDetails.asp?ProductCode=VWC-311-133-511-C

There really is no pressure rating for this filter, because it comes before
the pump. Note that it has an arrow on it, indicating the direction of flow.

Starting in '70, there was a bracket that fits around the pump body and
holds the filter above the pump, but that bracket isn't necessary, as long
as the weight of the filter won't pull the hoses off.

I have a couple round metal ones that Russ gave me that would also work.  

When you're running the fuel lines in front, here's what you've got: 
The feed line runs from the tube with the big nut on the tank to the filter
and then to the inlet of the pump. 

The outlet of the pump goes to the damper and then to the line on the
driver's side of the tunnel.

The line on the passenger side of the tunnel goes to a "Y" which connects
that line, the overflow side of the pump, and the plain
(return) line on the tank.

One more thing: On a restoration like this, I suggest that you install a
bypass hose between the 2 rear ends of the tunnel lines and pump gas thru
those lines for 10-20 minutes before you hook anything up to the engine.
That will flush out those lines. Dirt that comes out in this process will
end up in the tank and eventually get caught in the filter. This is better
than letting it get to your injectors.

BTW, when I bought my '68, new, the dealer replaced the filter at the
600 mile inspection. I figure they thought it might collect a significant
amount of junk in that time.

After that first replacement, I generally never replace the filters again,
unless something happens that suggests it might be necessary, like dirt and
water in the gas tank due to a broken overflow hose.

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

Thanks for the info.  Before Russ passed away he sent me a couple of CDs
with all kind of old dealer and aftermarket manuals on them. I found a
diagram on the whole fuel line set up. I printed that off and we have that
out in the shop to go by. Good idea on on flushing the lines. One hasn't had
anything in since 1984 the other since 1990.

Dennis