Alda is a fuel cut off device right? Whats the default setting when the engine is off ? No fuel or full fuel? I would assume cut off. And then as boost pressure increases the vacuum signal to alda increase allowing more fuel?

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I believe the alda is a fuel supplemtation device. it adjusts the fuel flow characteristics of the Injector pump to match the registered air pressure on a turbo motor.
John

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The ALDA simply limits the travel of the rack (and thus the supply of fuel) depnding on the pressure being supplied by the turbo.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

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But the off / idle setting would be restricted and then as the vacuum signal increases the rack is allowed to open more? If you have lots of black smoke at higher rpms does this point to not enough boost (o2) coming in?

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

The ALDA receives a pressure signal. I don't think the no pressure default is no fuel...just limited fuel.

If you have black smoke at high RPMs the you either have not enough O2 as you stated, or a different problem.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

thats what i meant. also whats the default for EGR? closed?

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

Default for EGR is sitting in a box in the closet....Sorry.

I guess I'll see this afternoon when I pull mine.

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

The ALDA serves to purposes. First it increases the maximum amount of fuel able to be provided by the IP proportionally to the amount of boost. It also is responsible for adjusting the maximum fuel limit in response to atmospheric pressure changes.

With no vacuum applied the EGR valve should remain closed.

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As ConnClark says, the IP is set to provide fuel as if the engine were under full boost all the time. The ALDA serves to modulate fuel between unboosted and full boost conditions based on a boost signal from the intake manifold. The ALDA has no influence on idle.

Smoke at high rpm could be oil leaking through the turbo.

Sixto
93 300SD 3.0

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine