Leaking carb (again)

My carb has recommenced leaking. I was testing the car up and down my drive today with quite a bit of throttle.
Once I had put the Landy back in the garage, I could see petrol dripping from the carb onto the manifold – not ideal.

The drip seems to start from the underside of the diaphragm. You can see in the photos:

1. The diaphragm has a shape where I think the leak is squeezing through, from the middle between two screws.
2. The diaphragm is also in two layers – I can’t remember if that is how it comes or it has become delaminated.

I did buy originally two diaphragms so I do have a spare somewhere I can fit, but I am wondering if this is a symptom rather than the issue.
I was careful when i installed the new one to make sure both surfaces were clean, but i could have another go. I don't know whether a bit of sealant would help or hinder.

If that bulge wrinkles when clamped it could certainly come through there. I've never needed sealant and you'd have to be sure it's not going to wreck the rubber - so I wish you well hunting down the other one!

ref the fuel leak, I cannot work out if there is supposed to be fuel one side of the diaphragm or it should be air. If it is air, then the fact the diaphragm leaks fuel is a symptom of something else that is wrong. If, however, it supposed to be fuel, then I “just” need to fix the leak.

I have read the simple technical description of the weber which includes “during the wide-open throttle condition the diaphragm spring overcomes the low manifold vacuum and close the by-pass air circuit” – it’s the “air circuit” bit which is concerning me.

I think you're confusing the diaphragms. That's the accelerator pump one, no air involved, and should only be wet on the inside.

boguing said:

I think you're confusing the diaphragms. That's the accelerator pump one, no air involved, and should only be wet on the inside.

Click to expand...

thanks for the info, that was exactly what i needed to know. I will have go fitting another diaphragm, as carefully as i can.

I had a similar problem with my Series II Solex carb.
Tested a new diaphragm but it still leaked.
The problem was the accelerator pump halves were warped (both parts). Sanded these plane (used sandpaper on the driver's window - great with flat windows...). After the surfaces were trued, no leakage!