ALDA: How can you tell if it's good for sure??? - PeachParts Mercedes-Benz Forum

87tdwagen · #1 01-04-2006, 06:19 PM

Hello All:

I just scoured the scrap yards and came up with a spare ALDA from a mid 80's 300SD, with the adjustment screw. I want to replace mt ALDA so as to have the unmolested original tamper proof and all. As far as I can tell my stock ALDA is fine, just wanted to mess with the enrichment now with the intercooler installed.

So I check my original on the car with the vac/pressure pump and get up to 12 psi, holds it. Should be OK, this is my reference. At the scrap yard found same one, tested the same way holds 12psi no issue on the engine. Take it off and compare again.

Now the piston travel in the older unit from the 617 is noticeibly more about 4mm total travel, on my 603 the travel of the piston is only half a mm or so, just enough for it to pop, but no apreciable movement in the piston body. I can't get the piston to move further even using needlenose.

The scrap unit's piston moves freely when pressure or vacumme is applied, the stock one just slightly, both hold pressure fine on or off the engine, Which set-up is correct?? I no longer have a reference

Thanks

Brian Carlton · #2 01-04-2006, 06:35 PM

I've never done the test as you have described, but it does not seem proper that the 603 could function properly with .020" of travel from the ALDA. This number appears to be way too low to enable proper fuel modulation.

I'll see if I can get Dave to respond to this thread. He's had them apart many times.

87tdwagen · #3 01-04-2006, 06:56 PM

Quote:

Originally Posted by Brian Carlton

I've never done the test as you have described, but it does not seem proper that the 603 could function properly with .020" of travel from the ALDA. This number appears to be way too low to enable proper fuel modulation.

I'll see if I can get Dave to respond to this thread. He's had them apart many times.

I also agree Dave would know these things inside out and no one has mentioned the piston travel in any of the threads I researched.

On another note, as to the main IP plunger that the ALDA activates, what kind of resistance should I expect. It now depresses fully but it seems like there is stiff spring resistance aprox 15 lbs. or so to depress. Is this normal?

I'm giddy because she currenty runs like a champ 9.8 0-60 times...apparently without the ALDA functioning??? Wonder what she's gonna do with it working right

87tdwagen · #4 01-04-2006, 08:20 PM

Well I installed the ALDA that provided the most piston travel and well what a difference the off idle knocks you back in the seat I luv it

Seems to hit boost a bit quicker now too, will keep testing and report back before and after 0-60 and 1/4 times.

Dave please let me know your thoughts on my earlier post.

Thanks

Jetmugg · #5 01-04-2006, 10:57 PM

Are the ALDA's interchangeable between the 617 and 603 engines? If so, my 602 might benefit from a 617 ALDA as well.

SteveM.

whunter · #6 01-04-2006, 11:43 PM

Look in

post Diesel Injection:

ShopForum > Technical Information and Support > Diesel Discussion
Organized MB DIY links post: Diesel Injection:
Organized MB DIY links

ALDA R&R disassembly, cleaning.

87tdwagen · #7 01-05-2006, 10:35 AM

Quote:

Originally Posted by Jetmugg

Are the ALDA's interchangeable between the 617 and 603 engines? If so, my 602 might benefit from a 617 ALDA as well.

SteveM.

Steve, the ALDA from the late 617 turboD cars are interchangeable with the 603 partnumbers are the same 1 427 133 150.

Best of luck

gsxr · #8 01-06-2006, 03:15 PM

Hi guys, sorry for coming to the party late!

I never measured ALDA movement, but I'd estimate that 4-5mm is about normal. Less than 1mm is NOT normal. Remember that the spring-loaded IP shaft moves upward for more fuel, and down for less fuel. The ALDA capsules hold it down (less fuel), and when pressure is applied to the ALDA, the internal capsules collapse under the pressure, allowing the shaft to move upward due to the spring pressure. If you remove the ALDA, you'll get full enrichment all the time. This would likely provide poor (and smoky) low-RPM performance, due to the over-rich condition. But there would be no additional high-RPM power, since the full load fuel is still limited by the internal rack stop.

Casey (Zeitgeist) was kind of the pioneer in this field in the USA on a 603 motor. His basic settings, from memory, are 1.5 turns CCW on the full load screw, and approx 0.75 turns (CCW, I think) on the rack minimum position screw (kind of an internal 'coarse' idle speed adjustment), then tweak the ALDA as needed to get it as lean as possible without power loss. More than 1.5-1.75 turns on the full-load screw results in the engine not wanting to return to idle, or not idling at all (engine RPM's way too high). That's when you need to send the pump to Myna Diesel in Finland, to get larger elements installed, so the pump can properly meter fuel and keep normal idle behavior.

Uh - this all assumes you have an intercooler installed, and an EGT gauge to watch. Doing this on a stock setup will likely melt pistons after 30-60 seconds of hard throttle!

87tdwagen · #9 01-06-2006, 03:23 PM

Quote:

Originally Posted by gsxr

Hi guys, sorry for coming to the party late!

But there would be no additional high-RPM power, since the full load fuel is still limited by the internal rack stop.

Casey (Zeitgeist) was kind of the pioneer in this field in the USA on a 603 motor. His basic settings, from memory, are 1.5 turns CCW on the full load screw, and approx 0.75 turns (CCW, I think) on the rack minimum position screw (kind of an internal 'coarse' idle speed adjustment), then tweak the ALDA as needed to get it as lean as possible without power loss. More than 1.5-1.75 turns on the full-load screw results in the engine not wanting to return to idle, or not idling at all (engine RPM's way too high). That's when you need to send the pump to Myna Diesel in Finland, to get larger elements installed, so the pump can properly meter fuel and keep normal idle behavior.

Uh - this all assumes you have an intercooler installed, and an EGT gauge to watch. Doing this on a stock setup will likely melt pistons after 30-60 seconds of hard throttle!

I cannot find where the 603 IP full load screw nor any documentation that shows it, you had a link to a pdf but it is dead. There is a hex shape screw at the top rear of the 603 IP that has a locknut and is paint marked, is this it? Or does the IP have to come out and remove the rear cover like on the 617? I'm lost, any help would be appreciated.

Bill

Doktor Bert · #10 04-21-2012, 01:02 PM

This is a very good thread...

Doktor Bert · #11 04-24-2012, 09:11 AM

Ok,

Pulled apart a spare ALDA and inside are (2) copper discs, that appear to be under pressure. There is an 'O' ring that seals the upper and lower halves and there is a smaller 'O' ring around the plunger stem on the lowermost copper disc.

That's it. No springs and nothing to really jump out at you.

Testing this ALDA I discovered the plunger moves out when vacuum is applied and the plunger retracts when pressure is applied.

The unit I pulled off my car leaked around the plunger and you could blow through it with only slight resistance. Although I simply replaced it with a better used unit, changing the 'O' rings is very simple.

I have found the best performance in my 300SD (after much experimentation) is 12 psi of boost, the ALDA all the way out CCW and 3.0mm shims between the ALDA and the pump.

Normal driving at 65-70 mph I am producing 10 psi of boost and the acceleration is remarkable for a 617. Shown is my boost gauge rigged for So Cal freeway testing.

I will post photos of the ALDA's internals later this evening...Robert