Please help lost without daily runner

I have a 1.5 JB engine running weber 36tlp carb. I have fuel coming out of the 2 holes on top of the carb which look like overflow holes for the float chamber. I have had it apart and the floats seems to be working ok. When i close it and blow down the fuel inlet i struggle. I have ordered a service kit but dont think this is whats wrong with it. Anybody had similar issues or know a fix for this. Is there a fuel pressure regulator on it somewhere? Or could it be a faulty fuel pump on the front of the engine. All help is appreciated as this is my daily runner and i'm lost without it!

Thanks

Lee