Works the opposite of the way you think it does. The design logic has the altitude compensator solenoid 12V energized at low altitudes, and de-energized at high altitudes (above 3,000 ft.)
Easy to test: With engine running at low altitudes pull off the solenoid wire and listen for (or feel for) the click. You may or may not perceive a difference in idle speed or sound.
The de-energized solenoid theoretically advances timing ~0.07mm.
Really a backwards way to achieve the compensation, as it is not failsafe-friendly. IOW, if the circuitry or wiring fails, that creates a normally overly advanced timing condition, potentially damaging the engine over time.
Setting injection timing for best fuel economy is not that straightforward for high mileage examples. Internal IP parts wear and can reduce IP internal dynamic advance range and action. One can compensate by advancing static timing only so far.
In my own experience, my own examples run well with good economy at .95mm static timing. With altitude compensator functioning as designed. And of course set while the cold start solenoid cable is temporarily disengaged.
To clarify, static timing is set while the engine is off. Therefore the altitude solenoid would be de-energized.
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1985 744 gle d24t
1985 745 gle d24t
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