Rusty fillerneck problem

Hallo guys!
I have noticed that my cabrio has a really rusty filler neck. Also I have had some problems with fuel starvation. Solved the problem by fitting a new stock mechanical fuel pump and blowing out the fuel lines with compressed air. Also tried to replace the fuel seperator bowl between the fuel pump an the carb, but for some reason this only made it worse. Worth mentioning that I have a Weber 32/34 carb.

Do you guys think that the problem with fuel starvation can be linked with a rusty fuel tank?

Do I have to replace the fuel tank?
Thanks

Evening I had the same problem I preplaced the filler neck tried to wash the petrol tank out, but in the end bought a new one works fine now.

Yep, rusty filler neck is bad, it will cause alsorts of problems, water will get into the fuel system if you use the car in the wet.
Replace filler neck and check inside the fuel tank then clean out fuel lines.

Treat and paint the new filler neck as the paint on it is just to stop it rusting away while on the shelf, once underneath the wheel arch and mud, stones and water thrown at it, it wont last 5 minutes.

Thanks guys!

Is swapping the tank for a new one a hard job? Expensive?

Not a difficult job to change the fuel tank if everything comes undone ok and is not rusted on.
The problem being is you have to remove the rear beam to get the tank out, you have to be very careful of the studs holding the beam to the car, shear them and you need to weld in new studs. A good clean of the threads and lots of soaking in penatrating oil will help.

I've just had my tank done and found the main issue was things breaking off when attempting removal. If your budget can take it get as much done as you can while it's all off anyway. I ended up with new exhaust, rear brakes and a complete waxoil to future proof it as much as I could.

To loosening old rusty nuts from rusty studs, clean threads with wire brush and lots of soaking in Plusgas or similar, (WD40 is not very good) for a good couple of days if possible.
When it's time to undo the nut, loosen a little then do it back up, loosen a little more then do it back up and so on….. this cleans the threads on the stud and stops the nut locking onto the stud.
But at the end of the day if the stud is weakened through rust it may break off what every you do.
When you come to put it all back together cover the studs and nuts in copper grease/ anti seize so next time every thing will come undone easily.  

I'm not really a fan of heating things up to loosen them but it seems to work for a lot of people.

Do I have to remove the whole tank if i´m just going to change the filler neck?

Thanks guys!

No you don't have to remove the tank.
If your petrol gauge is near the red area you can jack up the back enough for petrol not to come out of the fuel tank.
There is only 3 screws at the top behind a plastic cover underneath the filler cap and 1 bolt underneath the wheel arch. I found the hardest bit is removing the beather hose at the top of the filler neck.
If worth getting a new rubber hose between the filler neck and tank as you will find the old one will be brittle and hard. 2 new jubilee clips are also a good idea.
Make Sure you get the right filler neck as cabrio ones are different to tin top car, there is also 2 sizes of fuel tank, larger tank cars have a space saver spare wheel and a shorter filler hose, smaller tanks have full size spare wheel and a longer filler neck.

Picture to see what I mean.
This is from my 1988 Gti with a larger fuel tank, I used a tin top filler neck as I heard it will fit if you just cut is shorter but I found out it does not, I had to get it cut and welded to same angle as my old one.

Tin top filler neck with a smaller tank next to my old one.


You can see the angle is different


Cut and welded the end back on.



Painted with epoxy mastic then stone chip paint then underseal then waxoly.


Test fit before final painting.



Finish the underseal.


Fitted then the waxoyl.



My car is a daily drive and gets used all year round so that's why I went a little bit over the top on protection.