76 300D altitude adjustment - Mercedes-Benz Forum

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post #1 of 6 (permalink) Old 11-26-2006, 01:33 PM Thread Starter
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Vehicle: 1976 300d @460k
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76 300D altitude adjustment

I was paging through my 1976 300D owners manual and noticed the injection pump as a knurled nut which is used to compensate for changes in altitude. could this ability be used to improve mileage or performance by selecting a setting which does not correspond with my current altitude of 850 feet above sea level?

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post #2 of 6 (permalink) Old 11-26-2006, 02:49 PM
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Don't know what that screw do, but new diesels don't have one.
Attitude adjustment are not too popular lately. When I took my boat to Lake Tahoe at about 7000' -local mechanics told me that the only thing I should do is change the propeller to smaller pitch. There are no easy adjustments for engines on the market.
Popular advice is not too worry about elevations till you hit 3000-4000 feet, so you have not much to worry about.
I passed 10,000' in my wagon and driving slower on highways couldn't complain about lack of power.
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post #3 of 6 (permalink) Old 11-26-2006, 03:37 PM
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I think your car should have its own altitude compensating device, just like the N/A 300D w123. Is there an open hole right where the large circular dome is? That hole is opened to atmospheric pressure and will adjust to the altitude accordingly.

edit: I think the knurled knob you're talking about is the primer pump.

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post #4 of 6 (permalink) Old 11-26-2006, 05:10 PM
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The car doesn't have an automatic altitude adjustment or pseudo ALDA. There is a knob on the top rear of the IP for altitude. I don't have my car nearby for comparison but what are the increments?

1977 - W116 - 6.9
1974 - W115 - 240D /8 - 4(M) OM617.910 + Turbo + 300D FW - Completed 7/8/10
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post #5 of 6 (permalink) Old 11-30-2006, 06:36 PM
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Altitude adjustment

I have a 115 also. I live in Mississippi so i leave it at 0ft. Ive changed it around from 0ft to 8000ft, but cant tell the diff.
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post #6 of 6 (permalink) Old 11-30-2006, 11:32 PM Thread Starter
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when i got the car it was set to 8 thousand feet. i turned it down and the idle is smoother and the throttle hold knob can now be turned fully clockwise.
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