ALDA adjustment gone wrong, lesson learned...
 

Ok, I am young (17), and I want to rush through everything, and that can be costly, and I've learned my lesson today. I read the thread on how to adjust the ALDA on a OM617, and I just skimmed through it (BIG MISTAKE) and proceeded to try to loosen the screw without first loosening the locknut. The head of the screw split in two. I went back and reread the directions, realizing my mistake, so I loosened the locknut all the way, and I tried to loosen the screw a little bit with my pliers using the half of the screw head that was already there. I'm not sure if it moved, but it looks like it did a little bit. I found the other half of the screw on the garage floor, and if possible, I'll attempt a "screw repair" using some sort of "super glue". If that does not work, I may have to go to the MB yard and get a screw. But, I've learned my lesson, and that is to READ, and RE-READ. Oh well, :(
-Joe

READ THIS:
If you think you are going to be able to back the bad one out and replace it with another screw from a junkyard, you are wrong.

I figured that.
-Joe

What are you going to do with the screw from the junkyard?

Why Not
 

Why can't he replace the bolt(slotted head) with one from another Alda Unit...Just Curious

That's not just a screw. It is attached to stuff inside and the ALDA will break and be rendered useless if you turn it too far. Pictures of the inside of an ALDA are here, courtesy of gsxr.

benzoboy,

Here is a good lesson for you to learn:

If it ain't broke, don't fix it, take it apart or even touch it.

I have ALDAs for 15 years and 200,000+ miles and I have never touched one. And as far as I know, they are all working perfectly.

P E H

Truer words never spoken. Well, maybe someone has spoken truer words, I don't recall.

You might also say, "don't fix it, take it apart or even touch it" unless you at least know how to "unfix" it or put it back together. These old cars need enough work just keeping up with routine mainenance and repairs. Don't go looking for problems.

Rockin,

Thank you for your comment.

Did you see what d.delano wants to do to his MB?

P E H

Yes, rebuild it from the ground up. I got tired just reading it all!

If you can remove the lock nut without the inner screw rotating too much and messing up the aerobic chambers, you could cut a new screw slot in the screw with a Dremel and a thin disc. Might not be able to use a regular screwdriver in it, but a small narrow one shoud still work in the more "submerged" slot.

I've never messed with my ALDA either and I haven't looked at the screw you're talking about, but I know places like PepBoys sell kits for removing stripped bolts and they may or may not work for you. I think we all sometimes learn a lesson the hard way.

Problem is - it ain't a SCREW. It is a threaded shaft with a slot on the end, with the bottom welded to a sealed aneroid capsule. You might want to look at all the photos Rick linked to above. Here's one that should clear things up a little:

http://www.meimann.com/images/merced...LDA_apart2.jpg

what is the bolt made of? could he have someone weld/braze another bolt w/a head on it above the one that broke with out damaging the internals of the alda?

Coach,

I would think that the heat from welding would destroy the rubber or plastic parts inside the ALDA.

If he can turn the screw with a Vice Grip, why does the screw head have to be repaired? Set it where was and leave it alone.

P E H

I agree. If only the very tip snapped off, it can be adjusted with some difficulty, but still workable. Worst case you can get a used ALDA from Pick-n-pull for a few bucks and just replace the whole thing.

:cool:

Or if there are enough threads he can tighten two nuts together.

UPDATE:
Well, I took the half of the screw (well, it's actually a shaft) and just held it on the screw, and by the way it fits, the alda was NEVER adjusted, it's still in the factory pre-set position. So, everything is fine. It takes me 16 seconds to do a 0-60 run, but I can live with it.
-Joe

Actually, 16 seconds is pretty close to factory spec for a W126...! I'd try to tweak it a half turn or so CCW and see what that does. Or pull the ALDA and install a shim underneath, which has the same effect as turning the screw.

I'm afraid to touch that ALDA anymore! How exactly would you pull it and install a shim underneath? Also, I tried tweaking it anyway, but with a broken screw head, it's pretty unlikely I can get it turning, I even tried with pliers.
-Joe

You hold the ALDA and unscrew the large nut underneath, and the ALDA just comes off. There is a washer underneath. You can add another one, and vary the thickness to adjust the fuel enrichment. Photos of the procedure, and the washer, on a 603 engine are here:

http://www.meimann.com/images/mercedes/OM603_injection/

look for the "ALDA removal" links. Your engine is much easier because the intake manifold is not in the way.

:cool:

How does adding more washers increase fuel enrichment?
-Joe

The ALDA presses down on a spring-loaded shaft. Boost pressure makes the ALDA internals move upward, letting the shaft push up. Inserting washers moves the whole thing up, simulating boost pressure - same as turning the shaft CCW, which also moves the shaft up.

:)

Maybe if I can take the ALDA off like you said, instead of using washers to increase fuel enrichment, can I still turn the shaft CCW somehow once I get in there?
-Joe

where can you get those washers?

Nope, you can't turn the shaft with the ALDA removed - the ALDA would need to be disassembled. See photos at the link above, that should help clarify how it works.

for the washers, pull the ALDA and remove the washer that's in there. Then visit the local hardware store and try to find something similar in size (same ID/OD). Then you can file the washer to gt the thickness you need. I think something like 0.030" is equal to 2 turns of the setscrew, or something? I forget now...