Your ALDA device was set at the
factory by Mercedes and not intended
to be adjusted by mortal shade tree
mechanics (like me.) The purpose of
the ALDA is to sense the atmospheric
and/or turbo boost pressure and adjust
accordingly the quantity of fuel
delivered at a given throttle setting.

Most real techs do not like to discuss
this adjustment for several reasons.
First, it is an emission control. The
tech prefers home cooking and mama to
U.S. government accomodations. Second,
many experienced mechanics say that
10% (or more) of the time, when you twist
on an old ALDA, the fragile rubber
diaphragms inside are ruined. This is
VERY expensive to repair. Third, it
stresses the old engines, causes
excessive emmissions and can even wash
down the cylinder walls if you get too
aggressive.

Others advocate making this adjustment
to increase the performance. If
despite these risks, you loosen the
10mm locknut and turn the adjusting
screw 1/2 to 1 turn counterclockwise,
you get increased fuel delivery, if
all else is right with your engine.
There should be a factory seal on top
of the adjusting screw.

I do not recommend you perform this
adjustment. Your ALDA senses altitude
and adjusts fuel delivery for you without
need for adjustment. If you ruin your
ALDA in an attempt to hot rod your diesel,
it will cost big bucks to repair!

Darrell