Carb problem

[Ron Pier]

I have managed to diagnose a non starting issue to my MK2 to be that the float bowl is not filling. The float bowl shut off valve seems to stick up and the pressure from my modern electric pump is not sufficient to free it.
(The pump has worked fine up to the problem this weekend)

I've taken the top off and cleaned everything up and lapped in the valve, but still it has a tendency to stick up when operated off the vehicle and blowing through the fuel pipe by mouth doesn't free it.....Then it drops on it own or with a small tap.

So I went to Royal Kustoms and bought a new valve and found it's giving exactly the same problem. I can actually free it if I blow hard enough. I just don't understand why it sticks? I would think it should fall freely under it's own weight.

Any tips or advice regarding the pumps etc.
Cheers Ron

PS Carb is a Ford 94