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Discussion Starter · #1 ·
I believe that the ALDA on my '93 is bad, as it will not hold ANY vacuum and performance has been horrible. On occasion, that seems to be related to the weather the car will perform as it should, but not for long. I have seen a part listed as the "injection pump timer" and was wondering if this was the ALDA? Also, I have found a write-up on rebuilding a differnt style ALDA like found on my '87, and would like to know if it would work on mine as well.

I also have this funky problem with the driver's door on my '93. it takes two tries to open it. First try opening as normal, until the door does not fully open, then pull (or push) in the door until it clicks, then pull the latch again to fully open the door. It should also be noted that the same door's lock no longer functions with the rest of the car if the locks are actuated from the passenger door or trunk. Is this an easy lubrication/repair issue, or does something need to be replaced. And HOW?

Thanks in advance for any help.
 

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Hello cracker928:

Welcome to the BenzForum. Let's start with the basics of the ALDA system. The ALDA is a control systen designed to control the fuel delivery to the injection pump as the car changes altitude and also as the car goes through the turbo boost transition. There is also an overboost protection feature in the ALDA system. The ALDA itself is mounted on the injection pump. The altitude correction features of the ALDA are within the ALDA and normally require no adjustment or maintenence.

On the other hand, the boost signal portion of the ALDA do often have problems as the vehicles get older. The two most common problems are either a plugged ALDA pressure line from the intake manifold or a boost pressure leak due to a broken ALDA line. The blocked line is normally a result of carbon buildup in the intake from where the EGR valve introduces exhaust gases into the intake. The broken lines, a result of heat and age embrittlement.

Identify the alda lines on your vehicle and inspect them. One should run from the intake manifold to a valve (overboost protection switchover valve), normally mounted on the rear engine compartment wall, drivers side. If this line is intact, but black, remove it and clean it out with some carb cleaner. If broken, replace it. I just bought a new one for my 300SD (US$4.80). Be careful to not overtighten the banjo fitting when replacing this line. The hollow components of the banjo fittings are not designed for high torque.

The other ALDA line goes from the same valve on the engine compartment wall to the ALDA unit on the injection pump. Do the same for this line as the first.

Let me know how this goes before we go further.

-Scott
 

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Discussion Starter · #3 ·
Well, so far I have not found any leaky lines, and I have not found and overboost protection device. I thought I read somewhere that they were done away with on the 2.5 turbo. I DID find that the EGR was totally plugged up with carbon, and I pulled out enough carbon that wouyld amount to a golf ball in size. Checked the EGR for function and is OK. The manifold line to the ALDA and the banjo fitting are also clear.

The carbon removal did clear up my most recent problem of almost total power loss when the engine was hot, but the problems that make me suspect the ALDA still persist. Add to that another observation that while downshifting for power uphill, when the engine is revving higher, there is still little power, and the engine temp will creep up. This tells me that there is a lean mix.

Now one thing that I know I need to check is the injection timing. My brother had the timing chain replaced some time before he gave me the car. I have just been lacking an assistant and time to do that job.

Another revalation came to me while researching this problem. In my '87, the EGR can be totally bypassed without negatively impacting performance. This is largely due to the wastegate being pressure actuated. In my '93, the wastegate is apparently vacuum actuated, and controlled by the computer. The computer senses the EGR gasses and allows the turbo to provide boost. If there are no EGR gasses, the boost is disabled and you essentially have an NA diesel. So, when I recently had the no boost problem, and the low power off the line that prompted this post, I was getting REAL frustrated. At least I have my turbo boost back, and maybe some fuel efficiency.
 

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guys, what are the symptoms of a bad ALDA line?

Mine also has a "patch" fitting like the one on Scott's site.

I will definitely do that job described on his site this summer.

thanks much
 

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Discussion Starter · #5 ·
Wow, that was an old post. I didn't realize that I had never followed up. How rude of me...

Anyway, Willy, a bad ALDA line can sometimes be percieved as a "no boost" problem, when what is actually happening is a fuel starvation problem. The ALDA line is actually a pressure line, not a vacuum line, but the tests that Scott described work. When the manifold pressure is up from the turbo, the pressure is fed to the ALDA to compensate in the fuel mix. If the line is clogged, no boost is sensed by the ALDA and the extra fuel that is needed is not sent. It all sounds terribly complicated, but is actually much simpler than it sounds.

As for the results of my problem (from the original post), there were two problems working against me. First was yes, the fuel mix was lean, and has apparently been so since my father bought the car new. I used the ALDA to richen the mix (now too rich -I need to back it off a bit) and it solve my acceleration problems and my running hot problems (at higher rpm). The other problem that was working against me was a clogged center muffler. Now that that is replaced, more soot is passing through, showing how rich I am running. Just another thing on the honey-do list....
 

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cracker928 said:
I also have this funky problem with the driver's door on my '93. it takes two tries to open it. First try opening as normal, until the door does not fully open, then pull (or push) in the door until it clicks, then pull the latch again to fully open the door. It should also be noted that the same door's lock no longer functions with the rest of the car if the locks are actuated from the passenger door or trunk. Is this an easy lubrication/repair issue, or does something need to be replaced. And HOW?

Thanks in advance for any help.
Cracker, on this problem..get it figured out?

Might this be a check strap that needs replacing on the driver door? Prior to replacing mine, I had a similar issue. If I raised the door slightly (pulling it "up"), it opened smoothly. I could see the play in the check strap.

I am having a serious "creak" noise on my passenger rear door. I put some bicycle grease in there and am thinking to hit it w/some WD 40 here soon. Any comments w/your experience is appreciated.

Re the locks, if I open my passenger door it does not actuate the other locks, it only opens the pass door. If I turn the driver door, all locks are actuated when it is all functioning properly.

We obviously have different cars.
 

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Discussion Starter · #7 ·
No, I have not solved it yet. I am fairly certain that the problem lies in the lock/latch mechanism, but I just have not gotten around to doing anything about it.

Thanks.
 

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Rosamond is up in Northern Cali I believe.

If you are down in LA, shoot me a message if you want a guy that repairs the door handle lock. He cuts MBZ keys for very cheap--not many people cutting keys for MBZ so I hear.

His name is "Wilfredo" as I recall. He is located just north of Venice Blvd. on Sawtelle Blvd. or Sepulveda Blvd. on the E side of the street, a little drive up shack that sits virtually right in the middle of a huge parking lot that has a VONS (or some big supermarket chain).
 

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Discussion Starter · #9 ·
Nope, Rosamond is just north of Lancaster, barely out of LA county. Thanks, I'll keep that in mind if I find I need it. Actually, I do need another key cut...
 

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hwy 14, sure.

I want to say that it is "Sepulveda Lock & Key."

As I told someone in another post re upholstery, if you need to, call Beverly Coachcraft on Sawtelle in West LA and they will know the exact name of Wilfredo's shop. GL w/it.
 

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Discussion Starter · #11 ·
thanks.
 
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