cutting out

[philstar]

Hi guys, we have a Mk2 Scirocco that just won't hold idle, it randomly cuts outs. We have replaced the fuel tank, fuel pump, cleaned out the fuel lines, replaced the carburettor for a weber carb with manual choke, given the car a FULL service including many rolling road sessions but we cannot get rid of this problem. The owner is now considering getting rid of the car which is areal shame considering the amount of work that has been done, but she is coming to the end of her tether now.

Has anybody got any last ideas, or can recommend a specialist garage near to Redditch in the Midlands that we can take it to? I have been having a lot of work done at a local garage who are really excellent but cannot solve this problem.

[philstar]

The fuel return is blocked off but the fuel line is still going from the pump, through the swirl pot before it reaches the carburettor. I have not replaced the swirl pot, to be honest I don't really know what it does, I'm guessing nothing now that the return is blocked off?

[ianaudia4]

Worth changing the swirl pot as it may be full of cack.

[philstar]

Should I replace the pot or just remove it?

[bengould]

Remove it and put a restrictor in the return.

Ben.

[philstar]

OK cheers guys I'll give that a go and keep my fingers crossed.

[go-for-it1]

The swirl pot dampens out the mechanical fuel pump pulsation. There is also a filter inside. Bypass the swirl pot first with a "y" piece and make sure the return to the tank is restricted to 1.2mm so all the fuel doesn't just take that route. If this cures the problem either leave it or get a new original swirl pot. The replacement ones don't work well as the inbuilt restrictors are too big and allow to much fuel to go back to the tank thus starving the carb. Here is a post I did on this.
viewtopic.php?f=12&t=6115&p=42501&hilit=Swirl#p42501

[philstar]

Magic thankyou very much I will perform this work tomorrow chaps

[philstar]

Hey guys I bypassed the swirl pot as shown in the photo below:

https://gm1.ggpht.com/6DItRScRSy-KJEidP ... 8-h832-l75

I did not put a restrictor in the fuel return as it seems to run through a narrower pipe in a couple of places anyway.

I am still having the same problem, however it only seem to be after a 10-15 minute run on a highway, the car then fails to hold idle at roundabouts etc. I then switch off the engine or let it die, turn it back on and it is then fine again, driving around estate with lots of stop starts and no idle issues.

When I disconnected the first pipe from the swirl pot, there was a 'pop' as there seemed to be a lot of pressure in the fuel system. Is this expected? Someone has suggested running without the fuel cap on because there may be too much pressure, should the tank have a ventilated fuel cap?

Do you think I should go ahead and add the restrictor to the fuel return now? I am tempted to plumb the swirl pot back in again as there is hesitancy now when trying to overtake cars ie. accelerating hard from 60-70+ mph.

thanks for your help so far guys.

Phil

[philstar]

I should say, the fuel return hose was blocked off completely before I removed it from the swirl pot. This was a previous attempt to fix the idling issue and also the high speed stuttering.

[philstar]

I have just fitted a restrictor in the fuel return pipe but the car still tried to cut out, at the same place, about 15 minutes down the road at the end of a highway. I kept the revs up over the next couple of roundabouts and the car *seemed* fine for another 20 minutes or so until I got home. It does seem to start a bit easier now but the problem is still clearly there...

[philstar]

Just another thought guys, I recall the owner mentioning something about the brake servo having an air leak, I know that the manifold end is fully sealed up but would this still have an effect on the idle?