1975 240D w115 IP w/pneumatic governor
 

Can someone confirm my suspiciions?

This IP has a fairly large vacuum line running from the back of the pump to the intake manifold. I believe this is the altitude compensator for this pump.

If I connect a vacuum to the back of the pump where this line connects it will not hold vacuum.
Does this mean the IP diaphragm is bad and needs replacing?

This car at 3200 fet asl smokes mightly but at sea level does not.

It appears to be a straightforward procedure to replace this diaphragm but I would like to confim this before I pull the pump and tear into the back of it.

Thanks

Well, you got a lot right and a lot wrong.

The line in question is the load signal. Since manifold vacuum works against atmoshperic pressure I guess it is altitude compensation at the same time.

Usually when the diaphram is effectually leaking one can remove the oil adding cap and put ones thumb over the hole and the engine will change running speed. If the leak in the diaphram isn't that big then it is inconsequential.

thanks Steve,
That is a test that I would never have guessed in a million years...

The fact that the car smokes at 3200 feet and not at sea level would be some indication though would it not that the IP Diaphragm is not perfoming correctly?
Since the air at sea level being drawn through the manifold is naturally of higher density than at 3200 feet asl thereby in effect applying more "vacuum" force to the IP diaphragm.

Or would you attirbute this smoking/non-smoking to other items i.e. IP timing?

Or am I soooo far over my head that i should stop screwing around and find another hobby besides old diesels to play with...:D Please don't answer that question...;)

Sometimes the diaphram just looses its resilience and reacts different. I would replace it as they aren't that expensive. (well they used to be not that expensive.