Spitting Weber and over-fuelling

[h20hamelan]

Is there a different pressure if pump & or regulator fitted in boot than engine bay?
Thought the most common was pump in boot and regulator in bay and that was the less than 4psi.
But if you have both in boot, a higher 5 or so was required?

[Charles73]

Is there a different pressure if pump & or regulator fitted in boot than engine bay?
Thought the most common was pump in boot and regulator in bay and that was the less than 4psi.
But if you have both in boot, a higher 5 or so was required?

The regulator is mounted next to carbs, pump in boot….although it’s not easy finding room in the engine bay!

[Charles73]

I’ve found the time to give this another go…

I’ve measured fuel pressure and I’ve left it at 2.25 (on the lower side I know). I still had fuel leaking from the trumpets.

I then checked float heights again and they were slightly less than 8.5mm from underside of gasket to top of floats whilst upturned, so I corrected that but still had fuel leaking.

I thought I’d try reducing the float height from 8.5mm to 12mm just to see if that stopped the leak. I haven’t had a chance to drive it but no sign of any fuel leaks after idling for a few minutes (when the issue generally occurs). I know this is not the correct setting but could this be a case of ‘if it works then leave it alone’ or am I missing something? I may increase height to say 10mm and see how that goes.

To recap, the issue of fuel leaking from the intake and flooding is most prevalent on cold startup but once cleared the car runs well. Fuel pressure is fine and needle valves have been checked. Floats have been weighed and do not have any holes in. The carbs are DCOE 31 40.

I’d like to hear if anyone else has experienced a similar issue and what they did to solve it? Has anyone else had success in decreasing the float height from what is recommended?

Thanks

Charles

[ericbushby]

Hi Charles,
I prefer to measure the fuel level direct.
I remove the jet cover and remove one of the main jet stacks. With a dip stick and a small torch you can easily see when the stick touches the surface of the fuel, it shivers.
My S3 with Weber 151 carbs runs happily at 29mm from the top of the fuel chamber or measured from the rim of the jet cove allowing for the difference. My point is that you are not predicting where the fuel level will be, you are measuring it directly. The engine has to have run just before the measurement is taken so as not to have had any evaporation.
Best of luck,
Eric in Burnley
S3SE DHC

[Donels]

I had a similar issue on a twin weber equipped crossflow. Fuel was leaking down the outside of the trumpets. Cured with a little silicon on the trumpet shoulder during assembly.