This also was the case on my 1982 300D when I got it, and it made the pedal seem to have a lot of slack before you started getting a response. Putting new parts in made it drive much more responsively. It also seemed in danger of totally losing accelerator control because it would nearly pop all the way out.
I could not find the part here in FastLane. If you go to Performance Products (dot com) the part is called "Accelerator Pivot Mount" and for the 300CD is their part number 30-037 for $33.50.
The replacement part is much better in design and materials - it will outlast the car. You get the part that mounts to the firewall with two bolts, and the plastic bushing part with pivot that turns inside it.
I can't remember any spring - but I'll take a look at the car sometime to make sure.