Weber fuel return

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WreckTangle
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Weber fuel return

Post by WreckTangle » Sun Aug 11, 2019 8:41 pm

I have the seemingly common problem of fuel starvation with an aftermarket Weber carb on my 1.8 GT2 Auto. I’m in the process of implementing the welding tip fix which I think will solve the problem as folding the fuel return pipe over worked as a quick fix to get home. I’m trying to do this “properly”. Renewing the vapour separator made no difference so I have cleaned up the original, tapped the return spigot with an internal thread and slightly modified a welding tip to enable me to attach it to the return outlet. I’m expecting this to work, but I have been mulling over whether replacing the vapour separator with a low pressure bypass fuel regulator might be the “proper” fix since it would maintain consistent fuel pressure into the carb. Has anyone tried this or am I barking up the wrong tree?
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mark1gls
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Re: Weber fuel return

Post by mark1gls » Sun Aug 11, 2019 9:37 pm

I’d try the welding tip 1st and see if that helps...

Let us know how you get on.


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WreckTangle
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Re: Weber fuel return

Post by WreckTangle » Sun Aug 18, 2019 4:34 pm

Early indications are that the welding tip has cured the problem. About 60 trouble-free miles since fitting it taking in some long hills which seemed to bring on the problem before. However, I’m not sure I understand why. As far as I could make out the vapour separator has its own internal restrictor and will only send fuel down the return line if a constant flow of fuel is going through to the carburettor. Does the Weber require greater flow or pressure than the original Pierburg? Is the setup with a welding tip the best way to achieve what it needs?



mark1gls
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Re: Weber fuel return

Post by mark1gls » Sun Aug 18, 2019 10:15 pm

The problem seems a bit random, few posts on this problem on Mk1 Golfs as well and like the Scirocco not everyone seems to suffer with it.

Could be the fuel lines have slightly different internal bore size on some cars, fuel filters not letting enough fuel through.... etc...

The welding tip does seem to cure the problem 95% of the time...

Not 100% sure why it works but if it does happy days. :-D


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kidcrewbob
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Re: Weber fuel return

Post by kidcrewbob » Tue Aug 20, 2019 12:26 pm

Worked for me also - plugged hoses with a couple of appropriately sized bolts to start with and hey presto - runs like a dream. Can only deduce that the fuel return arrangement is just not required on a 1.8 with Weber conversion. Assume it's a Pierberg "feature"!



Nate
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Re: Weber fuel return

Post by Nate » Mon Oct 14, 2019 10:36 am

On my last mk2 I ditched the fuel return altogether to get it running happily. On the current mk2 I haven't touched it. It is weird


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e732lkv
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Re: Weber fuel return

Post by e732lkv » Tue Feb 04, 2020 3:24 pm

2 things to check, mechanical fuel pump and fuel sender located under the seat.
Probably the latter, I would take it out (caution patience) and clean the supply pipe which is immersed in the tank, this tends to clog up and you will notice at higher speeds, the car jerks or is starved of fuel while driving.
Hope this helps.

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WreckTangle
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Re: Weber fuel return

Post by WreckTangle » Fri Jul 17, 2020 10:33 pm

There has been no hint of the fuel starvation problem for months while I used the car for daily commuting (as a keyworker) during lockdown. However, earlier this week the problem returned when I let the tank get to about half full. I have been keeping it fairly full. Refilling the tank resolved the problem immediately.

I naturally assumed the fuel pickup would be the cause and envisaged a leak. However, it looks to be in perfect condition.

Any other ideas?

The filler neck is new and the tank has been professionally cleaned and appears to be totally free of debris, certainly in the area that can be seen through the hole where the sender unit goes.
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james butler
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Re: Weber fuel return

Post by james butler » Sun Jul 19, 2020 3:58 pm

one of the issues with a weber is the float height. it is designed to shut of the fuel flowing into the float bowl at a certain pressure which governs the fuel level.
if you weaken the pressure the level will be lower as it shuts off earlier giving the symptoms you describe.
upping the fuel pressure by increasing the restriction in the return means the fuel bowl will fill up more as it takes more pressure from the float to shut it off.
make sense?
another method is to bend the tang on the float pressing on the shut off valve but its not advisable, far better to up the pressure by doing what youve done with the welding tip as a restriction. you can also fit an electric fuel pump to get a more consistant pressure and flow although theres nothing wrong using a mechanical pump in good condition.
in answer to your last question sometimes the very end of the sender unit gets blocked sometimes where theres a little strainer.
i cut the end off mine so all the crap gets sucked up out of the tank and ends in the fuel filter thus gets removed on an annual basis when i change the filter.


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WreckTangle
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Re: Weber fuel return

Post by WreckTangle » Mon Jul 20, 2020 1:07 am

I did blow through both the feed and return parts of the sender unit while I had it out and it didn’t feel blocked at all. Had I found a split in the plastic pipe as I had been expecting my plan was to replace it with some suitable submersible fuel hose so I’m tempted to remove the filter end at some stage.

I am using a mechanical fuel pump but it is fairly new having been replaced by a previous owner. I did wonder about fitting a return style fuel pressure regulator in place of the vapour separator. However, since my longer term plan is to restore the car to stock condition I might put my energy into rebuilding my box of Pierburg bits into a working carburettor.