Scirocco Register

Could anyone inform me how full of fuel the inline filter should be when the engine is running?

I have a fueling issue and think that there isn't enough fuel in the filter to allow a steady flow. Also, does the filter have to be placed horizontally within the engine bay like the Haynes manual suggests?



Vehicle history:
+bought 3 months ago with new rotor arm, battery, ht leads, sparks and air filter. I did notice a few issues I still need to fix such as the filler neck leaking (could account for crap in the fuel tank...)
+had a running problem which was compoundly the coil and the carb flange which have both been replaced
+had a second running problem where the ignition would randomly die. Replaced the ignition module and things seemed fine.
+now have another running problem which is quite clearly a fueling issue as the car runs fine until I get onto the motorway at 3000rpm and it judders and splutters for 2mins before resuming as normal.

It probably won't fill up. As long as the level is higher than the tube on the output side it should be OK.

Ben.

What carb do you have, the original Pierburg or the replacement Webber?
I guess it's a Mk2 Scirocco ?

Yeah, it's a 1992 Mk2 1.8l EX with a replacement weber 32/34 with a manual choke.

I'm sure the level in the filter used to be greater than it currently is now I have the fueling problem. It's only just topping up enough to cover the outlet.

My next move is to take the tank out at the weekend which will give me an opportunity to review the state of the filler pipe and give it a general clean.

You could try and restrict the fuel return pipe, it seems some cars have a problem with to much petrol being returned to the fuel tank.
Some have fitted a welding tip in the fuel line to reduce the flow and seems to work, info in link and try searching the internet.
You can remove the fuel return pipe and cap it off at the carb and line to the tank (bit of fuel hose with a bolt or some thing in the end but make sure it does not leak fuel onto the hot exhaust manifold) and see if the car is any better then fit the fuel return hose back on with some sort of re stricter fitted.

viewtopic.php?f=12&t=14992&p=106274&hil ... rn#p106274

More info here.
http://vwgolfmk1.org.uk/forum/index.php ... nder-power&=

When I had my weber carb I replaced the swirl pot with a y connector and screwed a 0.8mm welding tip into the return side of it. This seemed to help a lot.
The level in the filter isn't as much of an issue as the level in the float chamber, as long as it's above the outlet. Check your float height is set correctly.

Ben.

It did look like the previous owner had blocked the return pipe from the swirl pot (vapour separator) by kinking the hose, which I assumed was part of a previous running problem. I have also replaced this with a brand new one as it was looking very corroded.

I don't entirely understand the requirement for the swirl pot, and why fuel is sent back to the tank - I have noticed quite a lot flows back as I have a transparent return pipe.

Is it recommended with the Weber carb to carry out such a crude adjustment???

Right, every day is a school day as they say....

The swirl pot is to remove air bubbles from the supply and ensure the carb gets a constant supply.

The floats on your carb actually shut off the fuel supply to the carb when the float chamber is full via a little valve on the fuel inlet.

At this point instead of killing your fuel pump, excess fuel is sent back to the tank.


If you remove the swirl pot you have to restrict the return or the fuel is supplied equally to the carb and the tank return. By restricting the return you are in effect forcing the fuel to go to the carb unless the float chamber is full and the valve is shut.

If you keep the swirl pot, the tank return is at the top and the feed to the carb is from the bottom. So unless the swirl pot is full, i.e. when the float chamber is full and the valve is shut, all the fuel goes to the carb. Having the same effect as the restrictor valve.

You will see this when under the bonnet as at idle the engine doesn't need very much fuel so most of it will return to the tank. If you hold the carb open and keep the revs high for a while you will see less fuel going back to the tank.


Hope this all makes sense.

Ben.

Thanks Ben. I think I'm understanding it now.
I'm used to motorcycle mechanics so I've never seen one before.

I'll have a tinker at the weekend!

i was told once that if your fuel filter is full of fuel then you need to change it, because as the filter gradually becomes blocked the fuel level starts to rise until it reaches a clear bit it can pass through again up until its completely blocked and you get a full filter and no flow.
so because you hardly have any fuel in your filter then its suggests its quite new and fuel passes freely through it like it should and to be honest this seems to be what happens on my car.

Problem solved now...
I removed the rear sender unit that sits under the rear seat and there was loads of filler pipe rust sitting at the bottom of the tank, and the small plastic filter was gunked up.
Cleaned it all out with a magnet and left it in the bottom of the tank with a tie wrap clipped into the sender and connected to the magnet so I can get it out again in the future.

The petrol to the filter was a constant stream again and the engine purred back into life!
Thanks for everyone's input on here, and I would recommend doing a simple check for crud in the tank with any fueling issues.