1966 230SL, Automatic.
Just curious about the construction of the Barometric Compensator (BC). I don't find a complete sketch in the Manual or on the Forum although the latter does provide several photos that suggest its construction. So here are my thoughts based on what I read and see. Within the outer can, there is a sealed bellows that is sealed against the top of the can. There is a spring within that bellows (that provides additional force to supplement movements of the bellows). Below the bellows and within the can, there is a pin that is supported by a lighter spring that simply holds the pin in the upmost position (against the bellows).
This pin protrudes below the bottom of the can and acts upon the fuel injection pump rack adjustment to adjust mixture. As outside atmospheric pressure drops (as indicative of higher altitude and less air), the bellows expands pushing the pin into the rack adjustment. This results with the FIP providing a leaner mixture to compensate for the thinner air at altitude. But where is the opening in the can for atmospheric pressure to enter the non-bellows area?
I removed my BC and it appears that top of the pin is measures about 21.33 mm from the base of the hex nut, so it appears to be operating properly - although testing needs to confirm this. But it doesn't appear to be "over-extended" which would suggest a leaking bellows. I have just felt that the car is running a bit rich. The gas mileage is around 17 on the road and I think it should be closer to 20. Plus the car smells a lot like raw fuel when first started. Maybe it's in this old head?
Thanks,
Harry