I've a beautiful powder blue 1980 240D that is unfortunately rusting
right out from under its paint, but otherwise only has 128k and the
frame is solid.  Body parts can be replaced like fenders and wheel
wells, but it's already been restored once from the ground up and I
believe the odometer.  The auto trans was shifting way too early and was
in 4th by 20mph.  Also, the car wouldn't shut off -- I checked for
vacuum leaks everywhere, and finally determined that the vacuum actuated
shut-off vacuum powered "solenoid" as either leaking or broken.  There's
a vacuum line that goes right from the heavy vacuum line to the brake
booster, and this line goes to one nipple on the ignition switch.  Then
another vacuum line goes from the ignition to the shut-off diaphragm
actuator.  When the key is turned to OFF, a valve opens and (pardon my
use of vacuum as a commodity) lets vacuum through to activate the
diaphragm on the actuator that then pulls hard on something in side the
injection block and the car DIES, DEAD, faster than hitting the STOP lever.

It hurt my back like hell to lean over the engine for 60 minutes, but I
got that vacuum actuator off and cleaned it out.  I sucked on it with my
mouth, and the bitter end, the L shaped hook that is supposed to grab
something important inside the fuel injection system pulled right down
-- but then slowly rose back up to the occasion.  I wondered if that was
right, found no documentation, pulled an identical unit off my parts
car, and indeed, the L shaped hook is supposed to stay pulled down with
just a tiny bit of vacuum.  Clearly, my diaphragm had a hole in it,
which would be bad news if I was female but in this case I simply
replaced the actuator and now the car shuts off with the key IMMEDIATELY
-- no waiting for 5 minutes for the fuel to run out.

Also, the transmission began behaving more normally, shifting up later
and holding gears at speed longer.  It's an entirely different car.

I might add that the problem didn't start until I began running B20, and
I suspect that the diaphragm is perhaps not too tolerant of biodiesel or
the alcohol inherent.  Old Rubber perhaps?

I'm going to post again about my tranny because I don't have a rod down
to my tranny -- I've got a vacuum line that runs down to the tranny.
The /rod/ that looks like it goes down to the tranny is simply a rod
that connects to a big spring that connects to a piece of the body.  So
all that adjustment mechanism and ball and threaded rod and nut and
rubber layers just for a big spring?  Am I missing something here?