at the bottom of the carb of my W123 M115, there is a hose that connects it to the diaphragm for the fuel return valve (at least that what the book describes it) to another point on the carb (which i'm not familiar with)

what i do know is that with that hose disconnected from the diaphragm, fuel drips down from that point but the car idles nicely.

with the hose connected, the engine sputters and can't hold idle well.

what does that connecting hose do and can i just plug the two points that the two hoses connect to stall for some time till i find another carb?

tks.