1975 240D Throttle question - PeachParts Mercedes-Benz Forum

AlexCole · #1 08-05-2008, 08:05 AM

Where do yall set the in-dash throttle control while driving?
When I start mine, it has to be turned fully to counter-clockwise or I have a rough start-up. When I'm driving, I turn it down somewhat to clockwise so that when I am idling (stoplight, etc) the oil pressure is ~35. The book says to turn it all the way down, but that causes a really rough idle, which may improve after DP and valvadjustment, just haven't got there yet. Alex

nhdoc · #2 08-05-2008, 10:55 AM

Quote:

Originally Posted by AlexCole

Where do yall set the in-dash throttle control while driving?
When I start mine, it has to be turned fully to counter-clockwise or I have a rough start-up. When I'm driving, I turn it down somewhat to clockwise so that when I am idling (stoplight, etc) the oil pressure is ~35. The book says to turn it all the way down, but that causes a really rough idle, which may improve after DP and valvadjustment, just haven't got there yet. Alex

The answer is you are supposed to be able to turn it all the way down once the engine warms up a little. The issue is whether your linkage and cable are adjusted properly to allow that or not...in other words is your car idling at the proper speed when turned all the way down? Without a tach all you can do is guess. If you have a tach or strobe you can set it to the spec which I would guess is about 700-800 RPM. I would say if it is idling rough then it is either too slow or you have an issue to resolve.

Diesel911 · #3 08-05-2008, 11:38 AM

Quote:

Originally Posted by nhdoc

The answer is you are supposed to be able to turn it all the way down once the engine warms up a little. The issue is whether your linkage and cable are adjusted properly to allow that or not...in other words is your car idling at the proper speed when turned all the way down? Without a tach all you can do is guess. If you have a tach or strobe you can set it to the spec which I would guess is about 700-800 RPM. I would say if it is idling rough then it is either too slow or you have an issue to resolve.

The above comments are true and a good place to start.
Find the type of IP/Governor combination you have before you adjust:
http://www.pauldrayton.com/uploadfiles/merc/Service/W123/w123CD2/Program/Engine/615/07-100.pdf
After that the rough idle could be cauesd by a small air leak in the suction side of the fuel systems, valves in need of adjustment, Fuel injector problems and Fuel Injection Pump timing.

pizzachef · #4 08-05-2008, 07:38 PM

In this warm weather, I don't have to turn the idle speed adjuster at all when starting. It might idle a little rough for a few seconds, but I hold my foot on the pedal like on the 300TD for a few seconds, and then its all fine.
I can't offer any advice on how to go about adjusting the idle or addressing the issues, just giving you my experience.