In the first schematic S66 is the electro-pressure sensor that communicates
boost pressure in the intake to Y30 (in the second schematic) via wire
which controls boost signal to the ALDA 103 (in the second schematic) via hard
plastic pressure [air] line.

You will note a hard plastic pressure [air] line from the pressurized Intake to
Y30,this provides the air pressure for the signal to ALDA 103.

SIMPLER: Y30 rides herd on the boost pressure (hard Plastic) air line from the
pressurized Intake to the ALDA 103.
If S66 tells Y30 the Boost pressure is too high,Y30 limits/restricts/disables
the boost pressure line to the ALDA103...Thereby preventing the ALDA 103
from fueling the Overboost.

NO BANJO BOLT on Intake 602.962
S66 might get gummed up by EGR/Oil Mist(from valve cover ventline upstream
of the turbo)
The pressure (hard Plastic) air line from the Intake to Y30[it's mounted on
a little nipple directly underneath Y30] might be subject to the same Goo-ing.

So far as I can see only four(4) banjo bolts on 124.128 1990 chassis:
three(3) on the Secondary fuel filter(Spin-on),and one(1) on the Pressure(air)
boost signal line Sensor for the EDS [the sensor is a 3''by4'' Aluminum box
(with the air line and Banjo bolt on the Battery side and an Electrical connector underneath)
directly in front of the Battery]

Did you see the LINK to the FSM (Holy Grail of Diagnosticians) bobodaclown
provided?Where it says Download, DO so.I believe the download is the FSM
schematics in a TIF format(which I haven't managed to open successfully ,YET)

Even if you do not download,you can use the manual.

Attached Thumbnails

   

__________________
'84 300SD sold
124.128

Yes I saw it yesterday, very good information.

I looked for that link but haven't found it yet. Could you share the link?

__________________
DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012

I hope this one works!

LINK:


http://mb.auto.pl/component/option,com_wrapper/Itemid,62/

__________________
'84 300SD sold
124.128