Alda maxed out? - PeachParts Mercedes-Benz Forum

d.delano · #1 09-13-2004, 11:25 AM

I was going to tweak the Alda ever so slightly just to see what happens, so I loosened the locknut and tried to turn the setscrew CCW but it wouldn't budge. I did not attempt to force it. I snugged the locknut back down. The cap has been removed, and the setscrew has about 3/8" thread sticking up above the locknut. Am I to assume that I have no further adjustment with this? Would it be wise to turn the setscrew back in for any reason? I'll post a pic later on.
My car has an acceleration problem, but only sometimes. Most of the time I can smoke traffic off the line no problem, but sometimes it seems bogged down, like when I slow down and then try to speed back up. It doesn't smoke very badly at all, can only see the smoke at night in the rearview in the headlights behind me. Oil press pegs at 3 at 1200rpm, 1.5 at idle. Temp at ~85C. Timing chain has ~2 deg stretch. Valves adjusted recently by myself. Little black particulate matter beginning to appear in prefilter, but there isn't much in there yet. Starts a little rough but smoothes out in a few seconds. I'm thinking that I will have to bite it and pull the tank screen, scrub it, do a diesel purge, and since the car is from the south add some biocide to kill the fungus that I'm sure is in there. The weird power behavior causes the transmission to shift weird too. What's everyone's opinion on this?

boneheaddoctor · #2 09-13-2004, 12:51 PM

Quote:

Originally Posted by d.delano

I was going to tweak the Alda ever so slightly just to see what happens, so I loosened the locknut and tried to turn the setscrew CCW but it wouldn't budge. I did not attempt to force it. I snugged the locknut back down. The cap has been removed, and the setscrew has about 3/8" thread sticking up above the locknut. Am I to assume that I have no further adjustment with this? Would it be wise to turn the setscrew back in for any reason? I'll post a pic later on.
My car has an acceleration problem, but only sometimes. Most of the time I can smoke traffic off the line no problem, but sometimes it seems bogged down, like when I slow down and then try to speed back up. It doesn't smoke very badly at all, can only see the smoke at night in the rearview in the headlights behind me. Oil press pegs at 3 at 1200rpm, 1.5 at idle. Temp at ~85C. Timing chain has ~2 deg stretch. Valves adjusted recently by myself. Little black particulate matter beginning to appear in prefilter, but there isn't much in there yet. Starts a little rough but smoothes out in a few seconds. I'm thinking that I will have to bite it and pull the tank screen, scrub it, do a diesel purge, and since the car is from the south add some biocide to kill the fungus that I'm sure is in there. The weird power behavior causes the transmission to shift weird too. What's everyone's opinion on this?

You are right to not force it. if it is already at the limit, you could try to shim it. Between the alda, and the IP

d.delano · #3 09-13-2004, 02:31 PM

here are some pics of the ALDA setscrew on my vehicle
does it look like it's out all the way?

DslBnz · #4 09-13-2004, 02:32 PM

Get faster burning diesel fuel, run D-Purge through the injectors, use Power Source products and pound the snot out of it provided everything else is N-Sync.

If you had a problem with the off-idle delivery, it would be constant ALL the time. Every station varies for good quality diesel fuel, of course.

This is all assuming that "smoking" traffic meant that you sped away and didn't literally dump a soot cloud over people's hoods. In which case backing off CW would be a GOOD idea.

BTW, seeing a wisp of smoke at night is perfectly normal. As long as it isn't significant.

gsxr · #5 09-13-2004, 02:42 PM

What is your 0-60 time (via stopwatch)? If the car is performing to factory spec, tweaking the ALDA won't do anything except waste fuel. That said, try turning the ALDA leaner (CW) to see if it turns easily, then go back CCW and see if it indeed is maxed out. If maxed out and you need more adjustment, you can either:

1) Try installing a shim instead, but remember that is limited by the internal full-load fuel stop... you can only add so much fuel via the ALDA.

2) Next up is the full-load fuel delivery adjustment, but on an OM617 that requires either pulling the IP off the engine, or pulling the oil canister so you can remove the rear governor cover - NOT fun. (It's easier on a 603!)

boneheaddoctor · #6 09-13-2004, 02:45 PM

Quote:

Originally Posted by gsxr

What is your 0-60 time (via stopwatch)? If the car is performing to factory spec, tweaking the ALDA won't do anything except waste fuel. That said, try turning the ALDA leaner (CW) to see if it turns easily, then go back CCW and see if it indeed is maxed out. If maxed out and you need more adjustment, you can either:

1) Try installing a shim instead, but remember that is limited by the internal full-load fuel stop... you can only add so much fuel via the ALDA.

2) Next up is the full-load fuel delivery adjustment, but on an OM617 that requires either pulling the IP off the engine, or pulling the oil canister so you can remove the rear governor cover - NOT fun. (It's easier on a 603!)

well said................I agree.

d.delano · #7 09-13-2004, 02:53 PM

I think maybe the safest thing at this point is to just make sure the fuel system is clean. The car will get out of its own way as it is, last thing I need to do is mess it up.

gsxr · #8 09-13-2004, 03:10 PM

Your 0-60 time should be rouhgly 13-14 seconds, below about 2500' elevation anyway. If it's much slower then something ain't right. Don't worry about screwing something up on the ALDA, if you don't force the screw to turn, it will be fine. Adding a shim also can't damage anything. The cars are MUCH more pleasant to drive - and have improved shifting as well - when the fuel delivery is properly adjusted.

OK - I just re-read your intial post. The smoking is normal, you'll *always* see smoke behind you at night in the headlights! First, have you disabled the EGR and ARV emissions junk yet? Start with that. Next up, it's time to pressure test your ALDA for leakage. You'll need a Mity-Vac hand pump. If it will pump up to 15psi and hold that pressure, or leak down slowly, it's OK. If you can't pump it past zero PSI, the shaft seal is leaking and could be the cause of the intermittent power loss. More details on rebuilding the ALDA (which isn't hard at all) are at the URL below. Note the comments about the shim are out of date, I now know it does do the same thing as turning the setscrew, I have to submit an edited article to Richard so he can update the page:

http://engine.articles.mbz.org/diesel/alda/

d.delano · #9 09-13-2004, 04:04 PM

hey, thanks!

Have not disabled EGR or anything yet. I'm taking it slow. I just wanted to see if a slight twist of the setscrew would yield an appreciable result. What did yield results was giving the thing a 750-mile Italian tuneup.
Will perform the vacuum test at the ALDA. If I should decide to rebuild it, what do I need to know about removing/reinstalling it? Are there any little springs or clips ready to jump out and bounce off my eyeball and get lost? Do I need to hold my face a certain way while I'm turning the wrench? I know the guy said the perimeter o-ring needed supplemental sealant. Exactly which brand/type and where can I buy it? Thanks for the help guys.