I've been renovating my XJ600 and at the point where it's all connected and ready to go. I tried starting it but there's no fuel getting through to the carbs. I thought it was a vacuum fuel pump problem but I've managed to replace this with an electric pump. Now I'm thinking it's the fuel tap but not sure why it's stopped working. There doesn't appear to be much fuel getting to the fuel filter. The vacuum pipe is connected correctly. Anymore ideas please?

is it a vacuum tap?

Try 'Prime' if it is.