76' 240D Loss of acceleration

My car has lost it's acceleration and this is a necessary item on a 240D. It's most noticeable when I am merging onto the freeway. The car will only accelerate slowly only after I hold the throttle pedal completely down and count to 10. It's as if no fuel enrichment is occurring. Yes, fuel pressure is fine - I run an electric lift pump. And yes, the linkage operates in the full range. Is there a load sensing rubber/metal diaphram on the back of the p-pump that could be cracked? I noticed a vacuum line going to it from near the throttle plate. This happened suddenly to an otherwise briskly accelerating engine with an immediate throttle response. Without a good service manual like a Haynes, I'm walking in the dark. Is it time to taking the fuel pump apart?

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Diesel Engine Specific Aid

diaphram..

Any chance you may have gotten some poor fuel and the filters are plugging? Any chance a line has loosened up somewhere and is letting it suck air?

To your question, yes there is a diaphram on the back of the pump. It is for governor control, something like an ALDA on later turbo models. It controls rack travel. The line you see goes to the intake manifold, make sure it hasn't cracked somewhere, that will slow them down alot(I have a 75 240D).

The diaphram is made of goat hide and they do go bad sometime. They are also not cheap and not easy to find, often only found from a Bosch dealer.

These usually offer some other signs as well. Often you will get more smoke, an uneven idle and surging at lower speeds under light throttle. They are not that hard to change but space is tight under that 115 hood. If you do change it there are some washers under the center shaft you'll want to make sure move to the new part.
Best of luck with it!

1977 300d slow acceleration

i had the same problem with my 240d when i first got it. at first i thought it was a major problem. i later had a friend help replace my freeze plugs when his nephew noticed my car was accelerating slow. he simply toped the transmission fluid, held the foot break down and went through all the gears. then he topped it off again and repeated the process till the car would want to take off while he ran it through the gears. he said that there is a void that the fluid wont go into until you run it through the gears and that causes acceleration to be hindered.