Do ALDA's ever go bad? yes!

[79Mercy]

This morning my 300D Turbo was extremely sluggish off the line, then after the turbo boosted it would take off pretty fast.

I thought hmm, i had adjusted the ALDA IN 1 turn a week ago to reduce the smoke a bit. So i stopped at the gas station and backed the screw out completely(where it was a week ago) and it was just as slow, or maybe slower than before.

I couldn't find a problem with the hoses being broken or clogged so i put on a ALDA that i got at the junkyard and everything was normal again. Hell it fells faster now then it ever has. 0-60 in 12 seconds

So yes, ALDA's can go bad, it seems rare though. Just thought i would post this in case someone else ran into a similar issue.

[scottmcphee]

The aneroid capsule(s) inside the ALDA can eventually crack, losing their atmospheric seal, and expand. This causes the ALDA to fail and depress the plunger on the IP. Result is an instant slug car off the line and it can even limit the fuel in the boost range, so I was having a hard time breaking 60 mph and turbo would only produce about 0.6 bar. This kind of failure is sudden. Happened overnight for me. My cure was to remove the ALDA completely. Car was hot off the line again and easily hit 1 bar boost and I guess I could reach 120 MPH again, but I chicken out before getting that high plus I don't want to force a head gasket failure on an already tender design.

[sethza]

um... what is an ALDA?

[Sev]

Originally Posted by sethza

um... what is an ALDA?

not hawkeye peirce from M*A*S*H, but that part that sits on top of the injection pump. i have some if anyone needs one. pm me

[Desert Panther]

Originally Posted by Sev

not hawkeye peirce from M*A*S*H, but that part that sits on top of the injection pump.

well, that definition really cleared it up for me. NOT!

[scottmcphee]

Originally Posted by Desert Panther

well, that definition really cleared it up for me. NOT!

search a million threads in here with "ALDA" and your car type... you'll find pix

[79Mercy]

Yeah mine failed over night as well, I got home from work last night at 10pm and then this morning it was absolutely dead off the line. And it wouldnt smoke at all, i knew it wasnt getting enough fuel.

[sixto]

It's a device that restricts fuel to the injectors until sufficient manifold pressure gets to the device.

Sixto
87 300D

[byronnash]

My car was slow and the ALDA adjustment was not turning. I just loosened the whole unit up to let the valve underneath move and it drives much better. The alda just kinda jiggles around in there. I do plan on replacing it once I can find time to get to a junkyard.

[scottmcphee]

Overboost protection is overrated for these cars. If you're worried, install a boost gauge in the dash. Or simply connect the overboost switch on the manifold to a light bulb on the dash.

[Orv]

FWIW, when I removed the ALDA on my '81 300TD I initially got a lot of smoke at full throttle at high RPM. Eventually I figured out this was because I was only getting 6 psi of boost. I used a manual boost controller to bring it up to 13 psi, and that eliminated the full throttle smoke.

I do still get smoke accelerating from a stop until the turbo spins up, especially when the engine is cold. If I accelerate crisply it's just a brief puff, and if I accelerate slowly enough there isn't much, but moderate acceleration from a stop sometimes produces more smoke than I'd like. Eventually I'd like to get a properly-shimmed ALDA back on there.

[Doktor Bert]

Interesting thread...

I always run my ALDA backed out full CCW. I discovered that it had 1.2 mm of shims under it, and I went out to a full 3.0mm of shims, each .75mm of shim seems to be about the same as 1 full turn CCW on the screw.

I also monitor boost and EGT and running 12-14 psi and 3.0mm of shims under the ALDA seems to give the very best performance, especially at 4400 ft/asl where I live.

One thing I noticed yesterday while going through my box of Benz junk...I have an ALDA that you can blow through, but will quickly seem to 'seat' some sort of valve inside. I am wornering if this is normal, or should the ALDA be like blowing into a vacuum advance' 100% resistance????

[Orv]

Originally Posted by Doktor Bert

I always run my ALDA backed out full CCW. I discovered that it had 1.2 mm of shims under it, and I went out to a full 3.0mm of shims, each .75mm of shim seems to be about the same as 1 full turn CCW on the screw.

Where'd you get the shims? I broke my ALDA by trying to back it off too far...now I have a good used one but I don't want to risk adjusting the screw, not knowing where it currently is in the adjustment range. The car can't get out of its own way if I install it set as-is, so clearly I need a pretty significant shim thickness.

[Doktor Bert]

I have collected them from junkers at Pik-N-Pull. I have also put a copper drain plug gasket on a felt tip pin and 'machined' it on the belt sander down to 17.90mm in diameter.

Each .075mm is about equal to (1) turn of the screw. Most ALDA's are set about 1-1/2 turn in from full CCW (out) based on the number of them I have adjusted personally...

Keeping the boost high at cruise seems to yield me the best fuel economy. I am never under 10 psi at speeds above 60 mph. You will notice a drop or reduction in fuel economy if you go too far on the ALDA...

[Orv]

Originally Posted by Doktor Bert

Most ALDA's are set about 1-1/2 turn in from full CCW (out) based on the number of them I have adjusted personally...

Yeah, if it still had the cap on I'd assume that...but this one had the cap removed, so who knows where it's set? I found out the hard way that it doesn't take much to shear off the screw when it reaches the end of its travel. There's no hard stop.