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1984 300D Turbo
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129 Posts
Discussion Starter #1
I do not know exactly what it would be called, but I am curious about it. Let me explain...

I owned another turbo car (although it was gas) but when I would depress accelerator, it was "light" feeling till about half-way down, then I could feel something else being moved from 50% - 100% throttle / pedal travel. Whatever this other weight I could feel through gas pedal was, it is what activated the turbo. I knew I would get no boost until gas pedal was at least 1/2 way and felt this extra linkage moving.

Now in the 300D, I do not feel any extra weight/linkage for turbo when pushing accelerator through its range of travel. The reason I am asking about this is I seem to get no turbo response until pedal is about 95% depressed, then I get a rush of power (like the trans kicked down to a lower gear, but trans remains in same gear.)

So how I have to drive the car on a higher speed streets is to punch pedal to floor (this seems to "activate" turbo boost) then roll back on throttle and feather it to meet traffic flow. If I try to drive normal, i get decent power until about 35% throttle, then it seems to bog/nail. This continues until I hit that 95% mark, then BOOM, instant power again.:confused:

Ultimately, I would like to adjust whatever that part or linkage is to allow boost to spool/come on sooner than almost floored. Is there any way to do this?
I have new fuel filters, tank strainer, and injectors. I think the bogging is linkage related, as the turbo/vacuum/fuel system are in great shape as well.

Any suggestions greatly appreciated.:bowdown:
 

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1981 Mercedes-Benz 300TD
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871 Posts
There is a fuel enrichment system called the ALDA and its located on the top rear of your injectoion pump. Its suppose to automatically increase fuel delivery as boost increases to avoid black smoke at the tail pipe. Sometimes the tube coming from the rear of the intake manifold to the ALDA clogs up at the banjo bolt on the intake and prevents the signal pressure from reaching the ALDA. Clean the bolt and the line and see if something changes. If not you can always adjust, or remove, the ALDA; I simply removed mine and love it.
 

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Registered
1984 300D Turbo
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129 Posts
Discussion Starter #3
There is a fuel enrichment system called the ALDA and its located on the top rear of your injectoion pump. Its suppose to automatically increase fuel delivery as boost increases to avoid black smoke at the tail pipe. Sometimes the tube coming from the rear of the intake manifold to the ALDA clogs up at the banjo bolt on the intake and prevents the signal pressure from reaching the ALDA. Clean the bolt and the line and see if something changes. If not you can always adjust, or remove, the ALDA; I simply removed mine and love it.
What was the effect of removing it completely? Did you go with a manual boost controller after removal?
 

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2013 MINI Copper S Clubman, '84 300CD-weekend car
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10,152 Posts
Your issue may be linkage related.

Have a helper press on the go pedal while you observe under hood. Engine off. look for any obvious problems. The rubber part on the firewall will sometimes crack and you don't see it until the pedal is pushed.

The ALDA is an automatic fuel restricting device, to prevent black smoke, it will restrict extra fuel not required. The signal is from the intake manifold, so turbo boost is measured and the aneroid capsules do their thing.

As mentioned, make sure there is an open path from the intake manifold pressure line to the switchover valve, then to the ALDA itself.

This will ensure the ALDA is receiving a signal. Some folks have bypassed the switchover valve, a redundant device, without ill consequences.

Some folks have also bypassed the ALDA altogether, if under wide open throttle you don't get much black smoke, unburned fuel, you're fine.
 

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