Fuel lines

[Scooter50]

I have a 1985 mk2 scirocco,I had been having intermittent problems with starting and stalling,the car had an original pierburg carb,I always had in mind that I would one day convert to a Webber carb so started with putting a Webber conversion on,still had intermittent problems,so lifted the back seats took the fuel sender out checked the tank for dirt etc looks very clean,so with thinking it’s definitely fuel starvation somewhere from the tank to the carb I swapped the supply feed with the return feed from the tank to the carb,(as the Webber no longer needs the return feed to the tank) and now the problem is 100% resolved,I have used the car now for the past two days with no problems.there is definitely a blockage from the original fuel pipe to the carb.I just wandered if anybody has had a similar problem and if there is any long term problem with swapping the feed/return lines.?
Regards Paul.

[C 20 CCO]

Have you tried an airline on the offending fuel line? If there is a blockage that may shift it!

[mark1gls]

Someone may of put the fuel lines the wrong way around before you had the car if you have always had the problem?

You could do with checking you have the pipe right and the feed pipe to the carb is the one on the fuel sender with a filter on it if you have that type of fuel tank as VW changed the fuel tanks 1984-1985, older tanks are smaller (you will have a full size spare wheel) and some are bottom feeders, later tanks are bigger (space saver spare wheel) and fuel pick up is via the top.

You should be able to blow down the fuel line to clear any blockages, you can do this with just your mouth if it’s not to blocked or you may need a little help from a pump or air line if it’s fully blocked. It’s best to re install the fuel return to tank line, if the carb gets to much fuel it’s got no where to go other than the hot exhaust manifold underneath which may end in tears.

If you re install the fuel return line and get running problems try to restrict the return fuel line with some thing like a welders tip to reduce the fuel getting back to the fuel tank. There is lots of threads on how to do this on this site and some Mk1 golf forums.

[Scooter50]

No,I have no access to an airline I did try putting a thin wire through but had no joy,my real question is will it be ok long term with the swapped fuel lines and has anybody come across the same problem,ie is there a kink or would it be a furring of the metal fuel line? as i can’t see any problems with the fuel tank.

[Scooter50]

Do I need a return feed to the fuel tank with the Webber conversion?

[C 20 CCO]

I tried the welding tip trick and my old timer neighbour plumber went nuts. He told me if it wasn’t designed that way why use it, there is obviously a problem that needs looking at. You know what? He made sense, the reason the fuel flow was weak was because the inlet manifold gasket was faulty. As soon as I swapped it out the fuel suction flow was way better and hasn’t faltered since. Hence removal of welding tip.
Don’t want to lead you down the wrong path but the moral here is to find the problem by systematic careful testing each section of the fuel system. Rather than modifying something that may help for a while but hasn’t fixed the initial problem.

[Scooter50]

Thanks for your reply,I do appreciate your comments,but I suppose my common sense approach is that if I do not need the return feed for the Webber conversion and can use that for the main fuel supply and it has fixed the problem without any long term problems then is a good permanent fix ?

[mark1gls]

Is your fuel tank sender like this?

https://vwgolfmk1.org.uk/forum/index.ph ... -confusion

If so and you are using the fuel return line to feed the carb you will run out of petrol before the fuel tank gets any where near 1/2 tank as it’s only a short pipe. Blow down the fuel line with your mouth and you should hear bubbles in the tank.

Yes it’s best to have the fuel return line plumbed in so the petrol has somewhere to go if needed.

[Scooter50]

I have swapped them over at the fuel sender so the main fuel line is now connected to the return on the sender and blanked off in the engine bay,and the return is now connected to the carb,hope this makes sense,my question is does the Webber conversion need the return?

[WreckTangle]

I think on these cars the feed and return are very similar so I doubt that of itself matters. I’d worry more about the configuration being neither stock nor in accordance with the Weber instructions. Unless you’ve declared that modification in detail to your insurance company then I suppose the worst that could happen is that the carb overflows onto a hot engine because the excess fuel has nowhere to go, starts a fire that causes a few million pounds worth of third-party damage and your insurance company refuses to pay up because of the modification. For this reason, and the engineering purity alluded to by C 20 CCO’s above, I’ve tried to keep mine as close to stock as possible on a 30 year old car. I think the Weber instructions say to replace the vapour separator with a restricted y-piece incorporating the original return line.

[Scooter50]

Good point,so it does need the return,looks like spanner’s out again and borrow a blow line from someone thanks for your help.

[C 20 CCO]

Keep us posted on how you get on, lockdowns have left us a little suppressed so conclusions are most welcome