My 1977 240D won't sustain a low speed idle. By that I mean that once started, the revs constantly increase until the engine is roaring. The car can only be driven by downshifting the 4 speed manual, forcing down the engine rpm's while also braking. An ungood condition!
The car also won't shut off. For that I suspect the vacuum diaphragm in the fuel injection pump. Are the problems interrelated?
The vacuum pump seems to be working since the power brakes are normal. There is no locking system so door vacuum lines, etc are non-existent.
From an aftermarket tech manual I see that there are two types of mechanical fuel pumps. One has a mechanical governor, the other type is pneumatic. Should I start my investigation there?
tnx,
Doug