Simon:

ALDA = altitude adjuster = boost pressure senor -- adds fuel as the barometric pressure and/or boost pressure goes up. Present on MB injection pumps since the late W115 chassis.

IP = injection pump, I'm lazy and use shorthand when typing! Fairly obvious, hard to miss the injection lines!

On the 601/602/603, the ALDA is a squarish box at the rear of the pump, sitting on top of a short stem. Has the boost line connected to it and a captive nut on the bottom and a hex collar so you can unscrew the captive nut. Made of aluminumn.

Peter

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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!