D3nhy

hi all, i have a 1989 90 with the 19j engine. Noticed that there's pressure in the fuel tank when i open the cap and so much so that tank leaks via the cap ive looked into it and it sound like afc diaphram needs replacing. I am meant to be out in it all day Sunday but cant if problem persists. Ive missed shops today so does anyone know if anywhere is open in Essex which might stock it on a Saturday? Any ideas would be gratefull. Cheers