Greetings All,

This question might be for the more experienced MB mechanic, but all are welcomed to provide their input. I have an '80 300TD wagon with an IP that has an altitude compensator on it. This car originally came from Calif. and probably had a use for this device, but the car now lives in Missouri. After reading the MB diesel manual on the engine and the IP and altitude compensator, it never does go into any detail at all about it's adjustment etc. My question is how can one test the compensator to see if it's properly adjusted for my location, or that it's not causing some type of adverse reaction to me pushing on the go pedal? I couldn't tell you if it's ever been messed with or misadjusted, but I'd like to see that it's not causing problems it shouldn't at the altitude that I am not located at. Any input or feedback as always is greatly appreciated and considered for repair or testing this thing out.

Thanks,

Charles

i.p. alda
 

Charles,
Most adjust the alda "altitude compensator" by checking for smoke out the tail pipe, yours is probably ok if you get a trace of smoke under hard acceleration.
To adjust you need to remove the plastic seal on top, which is very tedious with an exacto knife, dental picks, and tweezers. There is a lock nut and screw in there and you hold the lock nut and turn the screw out to richen.
This does not change much and you have a good chance of ruining the alda. If your seal is intact it's not been adjusted, Ca. emmission not in effect on your car.
Jerryb

Just one addition to what jerryb stated. I happen to mention to the parts manager at my local mb dealer that I was planning on adjusting the alt compensator (over 2 years ago). He warned me to be sure to saturate the adjusting screw with penatrating oil. He said that he's a few do-it-yourselfers and independent shops snap the adjusting screw. BTW, adjusting the compensator made a noticeable difference on my 240d.

Tell Me More
 

Greetings IMUL,

First off I guess I should say, that my altitude compensator is one of those round vacuum looking jobbies on top of the IP near the rear, and the adjusting screw is in plain sight on top of the unit, with a locking nut holding it in place. I'm not sure what the first reply post was talking about as far as having to disassemble or cut anything, just not the case to adjust this item. Where are you located IMUL that it made a diffence after you adjusted it? Which way turning the screw does what? Where did you notice the difference as well, from a dead stop accelleration, top end speed, hill climbing without losing speed, what? I'd appreciate any input you can provide, as well as how much the screw was turned, and whether you can tell if you've gone to far etc. Any written guidelines anywhere that you know of, to set this little fellow to operate correctly, or increase performance in one way or another?

Charles

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

Just Want It Right
 

Greetings Darrell,


On the contrary, I'm not trying to hot rod my diesel at all, that's a contradictory statement anyway. If I wanted a hot rod, I would have purchased a gas engine driven MB.
I just feel that because there is no seal of any kind on top of the adjusting screw or nut, that it's been fooled with by previous owners. From what I've seen so far, they could have screwed up just about anything just on purpose. I am just trying to put things right as they should be. I'd hate to be fighting an altitude compensator while pushing on the fuel pedal, and getting nowhere because someone got carried away with a screwdriver. Anyone know how it can be adjusted, or tested for proper operation?

Charles