Hello Tattedclacke,
I am not easy to get my feathers ruffled... but your "factory" drawing are
worse than BAVARIAN... Took me quite a
while to determine your "
GROUND" is the "
br" (brown)
wire emerging from your PUMP...
You have effectively
eliminated all other possibilities...
I don't understand why... but it APPEARS to return
to the driver area (no... not confusing it with fuel gauge)...
LOTS of opportunities for damage, corrosion or dirty
connections... !!
Since you were already
DARING ENOUGH to jump
the
BATTERY to the pump (I would
NOT try)...
testing the
GROUND might reveal your next quest.
Personally... (for wiring diagrams (factory is detached))
I would beg, borrow or
BUY the
BENTLY
book... or use a decent mechanics
SHOP manual...
Amazon com Bentley Paper Repair Manual VW Jetta Golf GTI A4 Automotive
I think you are almost there... (I would
NOT try)... but
Temporarily supply a local
GROUND for your pump ...
(I simply don't do ELECTRICS at the FUEL tank - EVER).
ELSE
I am attaching the "Do it Right" recommendations
from Delphi... (please read)
More Information for DELPHI FE0723
As you are already into the tank... you can likely
SEE
any issues with the fuel... However having BEEN THERE...
I would
STILL take the additional step of evacuating and
cleaning the tank...
Read & heed the above "Do it Right" ... I will
only add that cleaning injectors with Berryman
Choke & Carb cleaner has helped wash away the years of poor quality fuel.
Amazon com Berryman 0117 12 Chemtool Carburetor Choke and Throttle Body...
Hope this helps
Carnac the Magnificent