Hi there,
Your vacuum tank couldn't possibly cause your problem. Ditto with the charcoal cannister. The problem must be that the float needle and seat are not seating. This could be due to a damaged float, or a worn needle/seat valve, or contamination. If you take the bottom cover off the carburetor, you will expose the float, needle and seat. Carefully remove the float pivot, and unscrew the needle valve assembly. Make sure that it seals completely with a very light pressure on the needle. Make sure that the float has no holes and really does float. You can test this in a pan of water, also it should not have anything in it if you shake it. The floats on my Jag are made of brass, but if your float is foam, be aware that foam becomes saturated with fuel over time and doesn't float anymore. There is a fuel screen behind the carburetor's fuel inlet fitting. Remove the fitting and the filter screen, and make sure it is in good shape! Make sure that the float aligns with the base of the carburetor when it is turned upside down - the float should be about level when the fuel level is correct. There should be about .65 - .67 in. clearance between the float and the body of the carburetor. (16.5 - 17mm) If adjustment is required, be sure to only bend the little arm that contacts the needle. Both sides of the float should be even, and the float should not rub on anything. After assuring yourself that all parts are clean and gaskets are good, reassemble the carburetor. I think this should take care of your problem. By the way, you haven't replaced the fuel pump recently, have you? A too-high fuel pressure will cause big problems with this carburetor, it is designed for about 4 psi only. For example, if you got hold of a high pressure pump designed for fuel injected engines, you would most likely end up with a flooding problem. My Jag book has a very complete rebuild info for this carburetor (175CD2SE is what the Jag uses, same carb but throttle linkage for two)
Good luck with it,
Richard Wooldridge