TClanton:

ALDA = altitude adjuster = fuel regulator for increased boost. As the pressure in the intake goes up, the ALDA causes the IP to deliver more fuel.

The banjo bolt is a hollow bolt that holds a fitting shaped a little like a banjo, also hollow, to which is attached the hard plastic line that connects the intake manifold to the ALDA.

MB has an overboost protection device consisting of a pressure switch on the manifold and an electrically operated valve (the switchover valve) connected to the boost line between the intake and the ALDA. If there is too much pressure in the manifold (if, for instance, the wastegate in the turbo sticks closed), the switch will close, and that opens the switchover valve, venting the boost and reducing the fuel delivered so the engine won't blow up.

If the banjo bolt is clogged, which happens fairly often with age, the swithover valve (rectangular box, usually on the firewall) is bad and always vents the boost (typical failure mode), or the lines are leaking at the little rubber ends or are broken, you will have very low horsepower since no extra fuel is added.

Ditto if the turbo is bad (another long description -- check the boost lines first).

Hope this helps -- diesels are very different than gasoline engines -- not hard to work on or figure out, just different!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!