That is BIZARRE. I've never heard of that before. Try pressing down on the center rod which is now exposed with the ALDA removed... it's spring loaded, and should move freely (it takes quite a bit of pressure to move it, but it shouldn't bind or stick).



Yes, you can buy a new ALDA from Bosch, but you won't like the price. Snag a used one from a Pick & Pull... the OM617 ALDA's are the same as the OM60x. They pop up on eBay from time to time as well. It should be pressure tested though, to test you screw it on to the IP, and apply pressure with a Mity-Vac. It should pump up to 15psi and hold pressure steadily, or leak down slowly (say, 1 psi loss per second). If it leaks so badly that you can't pump it up to 15psi, the shaft seal needs replacement. Jim Friesen sells replacement seals so you can rebuild it yourself. I still would like to know how yours failed... if one of the aneroid capsules ruptured, it would provide more fuel, not less. Photos of ALDA internals are on my website at this link.



Yes, the ALDA is calibrated on the pump, on the calibration stand, then sealed. Afterwards, it can be adjusted via shims beween the IP and ALDA. Or you can remove the tamper seal and adjust via threaded rod. This adjustment can be done via calibrated butt dyno though, the test stand calibration is not required.



Well, something ain't right, that's for sure. Try using a screwdriver to press in the hole on the bottom of the ALDA. It should feel "springy" as the aneroid capsules compress. I'm not convinced your ALDA is toast, but I'm also not sure exactly what's going on here...

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

The pin moves up and down freely... not a huge amount of travel. When pressing down while the engine is idling, idle drops a tiny bit.

With my mode of failure, the ALDA must have somehow jammed the IP pin down. I'll sort thru my existing ALDA unit this week and post my findings. There is a definite, firm, springy resistance if I push into the ALDA with a screwdriver.

Also, now with the ALDA removed, the turbo boost pressure goes up smoothly. (I guess this is the way it is supposed to be, as I had no point of reference for comparison) Previously, in the no power situation, there would be little or no boost below 2800 RPM (< 3PSI). Then at 3200 RPM, boost would swing to 10-12PSI. Car would have a noticeable increase in power (still way underpowered) at that point.

My experience with boost on my SDL is that at about 1800-2000 RPM I get 2-3 PSI and I get a rapid boost increase with RPM's after that up to 12-13 PSI at 2200-2500 rpms.
EDIT - Misread your previous post- "Seems like your boost is lagging as though you have a restriction or turbo issue." I see you are getting smooth boost - I don't see why removing ALDA would allow better / correct boost?
I still think you may have a fuel issue also - air -perhaps.
If you are not getting full boost until 3200 RPMs then you have a problem other than the ALDA.

EDIT - My ALDA pressure port was completely clogged and I saw no real problem.
EDIT - Misread your previous post- "Seems like your boost is lagging as though you have a restriction or turbo issue." I see you are getting smooth boost - I don't see why removing ALDA would allow correct boost?

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

Correct - there should be a smooth power increase as RPM's increase off idle. There should NOT be any "kick in the pants" as boost suddenly builds. If there is, the ALDA is adjusted too lean (IP low on fuel delivery off idle).

On a properly calibrated pump, removing the ALDA entirely wil provide too much fuel off idle, as evidenced by a significant amount of black smoke whenever you hit the throttle from a dead stop. When adjusted properly, there should be just a slight puff of smoke, visible in sunlight (don't try to view this at night in the headlights of the vehicle behind you - can be misleading).

I am missing why the removal of ALDA would make achieving smooth (full ?) boost at lower RPMS?
Is this simply because you are able to produce full output from the IP and spin the turbo up faster?
If you were able to get to 2500 RPMS previously and not get full boost , why would removing the ALDA create full boost and smooth boost at lower RPM's?

My understanding is that the ALDA is a pressure driven IP enrichment device.
If you remove the ALDA you are simply increasing fuel output at any given throttle position.
Wouldn't the turbo still perform the same way at a given RPM level and wouldn't you simply be providing more fuel earlier or sooner by throttle position.?

Forgive my ignorance of turbo thermodynamics.

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

Remove the ALDA shifts the entire fuel curve upward (richer) including off-idle power. More fuel = more power with less throttle movement.



Exactly correct. But remember that the fuel delivered is still limited by the governor. You can't get max fuel off idle because the RPM's are too low, and the governor modulates the fuel delivery based on RPM, throttle position, and ALDA plunger.



The turbo needs a load present (power prodcued) to build boost. That's why you get no boost if you rev the engine in Park or Neutral. The more fuel delivered, the more load which can be created, and more power can be produced, therefore more boost (and more power) at a lower RPM.


One of the more interesting tests to try on your personal car is to time the car from 0-60 with a stopwatch. Then, disconnect or plug the signal line to the ALDA (but leave the ALDA installed!) and test the car again from 0-60. The car will be slower with the ALDA signal blocked, but not off idle. The car should still pull off idle just as strongly with or without the ALDA connected. The difference is, with the ALDA disconnected, the power from roughly 2500rpm-up is reduced, and the car will be slower. But it shouldn't be a huge difference... on my car, it was about 10 seconds with ALDA connected, and 14 seconds with the hose removed. If your car is drastically slower (say, 18-20 seconds) with the ALDA disconnected... either the IP needs the ALDA shimmed or adjusted, or the IP needs the full-load setting increased, or both. When properly adjusted, the car should not be any faster with the ALDA removed, compared to having the ALDA installed and functioning properly.

Thanks for the explanations - the at load requirement to produce boost is something I will not understand until I read more on turbos.
The test you recommend is interesting and something I will try. The "full-load setting" you mention as an adjustment - is at the IP on the governor - 2f in image? I don't think that's something I would want to do. Looks like an IP test bench adjustment.
Regards,
Chuck

Attached Thumbnails

 

__________________
1986 300SDL 201K Daily Driver
1984 300D In Progress
1989 240GL 196K Swedish Brick
1984 300SD -- Sold 289K
------------------------------

I still don't fully understand it, but I know that's how it works.



Yes, the full load setting is adjusted via 2f, and yes, this is normally done on a calibration stand. However, if your pump is working ok on the car now, you can carefully increase this from the baseline setting. If you diassembled the pump, then it would have to go back on the calibration stand to get back to the baseline. Anyway, when adjusting 2f, this shifts the entire fuel curve upward (richer), off-idle to redline. That means if your ALDA was adjusted properly before, it will be too rich after you increase 2f, and it may need to be leaned out. Also, when adjusting 2f, you'll also need to adjust 2b (coarse idle) and possibly 3 (fine idle), then adjust all throttle linkage rods as well to ensure they don't restrict either the idle or WOT positions.

If you turn up the full load, you can get up to a 15-20% power gain, but this isn't recommended without either a permanent EGT gauge or intercooler, or better yet, both. I've been running my '87 like this for a few years now with no ill effects. Dyno testing showed approx 170hp at the crank compared to 148hp stock. If you want more power (beyond the 15-20% gain possible with the stock pump), the pump must be modified with larger elements ($$$$), along with intercooling and aftermarket gauges. I've got a shop working on a modified pump but it's not completed yet.

Back to the saga... put the ALDA back on the car tonight... pumped it up with my new mityvac... it definitely holds no pressure.

The fact that the ALDA can see no pressure and the car having zero power makes some sense to me: if the ALDA sees no pressure, fuel will never increase. On my IP, the basic position of the rack with the ALDA installed must be very lean. I confirmed this by wedging the pin down on the IP, and trying to drive... no power. The stiffness of the spring in the ALDA seems to be enough to hold that pin down all the way; perhaps there is something additional broken in ALDA which keeps that pin down further than normal w/o pressure, but I don't know as I can't get the screws out to disassemble... likely need a larger screwdriver and a decent vice.

Also, without the ALDA, the car smokes pretty good, both at idle and immediately off idle. It definitely jumps right off idle. All the power is in the 1st 1/4 of pedal. Transmission is confused.

Anyone have an ALDA available? Thanks for everyone's feedback and help.

as ever
Paul

Pretty likely to be a bad shaft seal, although there could be something more going on. BTW, did you ever verify that boost pressure was being delivered to the ALDA, by connecting a pressure gauge while driving?



Correct - if the ALDA sees no pressure, fuel will never increase. That's why I asked if you verified that boost pressure was being delivered to the ALDA. Even if the ALDA is leaking (won't hold pressure), this normally will only affect part-throttle power. The reason is, the turbo can provide far more airflow volume than the ALDA can leak, so pressure does build inside the ADLA, and full-throttle power should be normal. But yes, on your IP, the ALDA is definitely pushing the pin down too far in the "basic" position.



Yep, both are usually required. The screws have threadlock on them, so some heat may be needed to loosen 'em up. They are really tight.



YES! This is EXACTLY why I don't recommend leaving the ALDA removed. You end up with an over-sensitive throttle and screwy transmission shifting, besides the smoke and reduced fuel economy. People who claim it works great on their cars most likely have an IP that needs a full-load adjustment.



You just missed one on eBay for $25... click here...

Does your 87 have the "trap oxider"? If it does it could be plugged -- I had a 87 300D turbo and it became a common problem until after the "plumbing" was modified by Benz-- at their expense.

just a thought

3pointstar

__________________

Yeah, I had my boost gauge tee'd in between the Y connection and ALDA... this is how I noticed nearly no boost until 2800 RPM and then a huge swing to 10PSI at 3200 RPM when I was initially debugging this thing. Now the boost gauge is connected in place of the ALDA (and the boost pressure is smooth and steady).

this indicates that pressure is now rising smoothly as it should because fuel is increasing smoothly due to a properly functioning ALDA. What is the highest pressure you are getting though? I have seen a case where the flapper in the exhaust that controls the turbo was partially open and initial boost would not come on at initial acceleration. This is often accompanied by a plugged Trap, seems the carbon builds up all along the exhaust up to the trap, including the wastegate, this is just another little issue the 603's can have and its hard to get 10 psi in that case. I think you should see boost run 13 psi to 15 psi. it varies from one car to the next though.

__________________
'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!