Mk1 [tech] - Addition of pre-pump?

[drew@scirocco.cs.uoguelph.ca (Drew MacPherson)]

The biggest issue to resolve will be if the later style sender (with 
transfer pump) uses the same tank fitting as the earlier style sender 
only.

I expect that this is the case.  The next challenge will be fitting the 
transfer pump into the tank.  The 84.5+ cars have a slightly larger tank 
with a small dish at the bottom where the strainer for the transfer pump 
collects fuel from.  IIRC the transfer pump assembly on the sender is 
spring loaded to ensure that it sits on the bottom of the tank (I know 
this to be the case with A2 transfer pumps, but it's been a few years 
since I replaced the one on the scirocco.)  It may be necessary to modify 
the transfer pump or the line that connects it to the sender in order to 
allow the pump pickup to sit at the bottom of the tank.  Also, a number of 
pre-84 A1 tanks I have been into have baffles in the tank around the 
pickup tube (which runs out the bottom front corner of the tank)  It may 
be necessary to find an aftermarket tank (without these baffles) or remove 
them (not sure if this is possible without destroying the tank.)  The key 
is to ensure that the pickup strainer sits as close to the bottom at the 
lowest part of the tank.

You will also need to block off your current feed and return connections 
on the tank and re-plumb your fuel lines so that the transfer pump routes 
to the main pump (good idea to put in a small resevoir or later Scirocco 
"filter/resevoir" to keep the main pump from overrunning the transfer 
pump) and the return line goes to the top of the tank.

Does this help at all?

Drew

On Mon, 17 Mar 2003, Benjamin Harder wrote:

> AFAIK, none of the mk1 rocco's came with a fuel pre-pump installed.
> I would like to know (besides wiring issues) what, if any, issues there
> would be to install a pre-pump?
> 
> The main reason for asking is an experience I had with my former '81
> while autocrossing... I had about 1/4 to 1/3 tank of fuel...
> coming around a long sweeper (left-hand turn) and then onto a straightaway
> the car would starve itself for fuel and sputter.  Not good while trying
> to race!  So, the issue was obvious to me... the car really needs a 
> pre-pump, or of course just a full tank of fuel... which isn't always
> the best idea on the track...
> 
> Anyhow, any experience with this one would be appreciated!
> 
> 
> =====
> Benjamin Harder
> 86 Scirocco 16v
> 80 Scirocco (new engine is almost ready!)
> 93 Passat GLX
> 
> http://www.geocities.com/vwtype53/
> 
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