hello all. my 1.8 on a weber was running top noch in november/december last year in the cold weather, after i installed a carb heater. all of a sudden it turns january and car runs like a bag of sh*te again. When cold needs choke, but then the choke is too much - so u let it in a little then it isn't enough (no inbetween) what i did notice is that when looking at the carb, on the right hand side behind the throttle linkage is a like a brass-ish disc/diaphram unit, has a black hose coming out of the back, and like an arm on the front. Well last year the arm on the front of the diaphram was all the way up when running. it is now currently sat on the stop (constantly down) so which should it be, up or down, and also what is that unit for? all the best, Dono
It is a vacuum diaphragm that opens the choke slightly upon startup. When you pull the choke out before start up, the choke lever contacts the fulcrum lever and thus pulls the diphragm out. When the engine starts, vacuum is created, the diaphragm is drawn towards the vacuum source and the fulcrum lever knocks the choke lever down a bit. Just imagine that the pipe on the back is sucking (not blowing) and operate the mechanism by hand, it'll soon become clear what it controls.
