I know how to adjust the idle speed on my '83 300SD(long screw on side of injection pump)but the engine will not idle when cold. You can go ahead and drive it with the engine cold. It just will not idle when cold. Idle speed when warm is around 900RPM(tach. does not work.)Car runs great and idles fine after it warms up. How do I get it to idle properly when the engine is cold? There is no knob on the dash to adjust idle speed like the earlier MB diesels had. Bill L

First let me say that the idle speed is not meant to be owner or shop adjusted.
But if it has been adjusted and runs ok warm, you might have a damper pin/screw thats in too far.Pin is gold colored in the late type,ealrier version is silver. The pin is the 12 mm hex at the rear of inj pump. 14 mm lock nut. loosen the lock nut and back out on the damper screw with warm engine at idle. at some point it will get very rough idling. at this point slowly turn the screw in just until it stops shaking. then lock it down.
Then recheck for cold stalls. The idle speed should be 750 RPM hot or cold, and is controlled by a centrifugal mechanism inside the injector pump.

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Michael Haven CMAT,CMM,L1
MPH Automotive Services
16510 Park Row
Houston, Texas, 77084
281-579-8885

I will sometimes remove the screw that Michael is speaking of and inspect it. The outer tip should be convex in shape. If it is concave, it should be replaced. I would start there. Also, I'd replace the fuel filters and blow out the strainer.

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Benzmac:
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