Rough running M186.. Help Please! (Adenauer Content)

[mabbonizio]

Hi Folks,

I realize there are not many forum members with Adenauers but am hoping that someone who has worked on one, or just has a good knowledge of older cars with Solex carbs can chime in.

I recently had the motor in 1954 300B Cabriolet rebuilt. Prior to the rebuild the motor ran flawlessly, started immediately, but had a knock. After the rebuild the knock is gone and motor runs OK. It can be very hard to start when hot and usually requires me to press the accelerator to the floor.

It fires up just fine when cold but after a few seconds begins to stutter. The idle fluctuates from high to low and if revved will choke a bit.

If I tried to simply drive off the motor will bog down and cut out, however if I let it warm up a bit it will run and drive ok but idle rough. Additionally if I try to climb a hill in say 3rd gear at a low rpm the motor will bog down and cut out. It is VERY jerky at low rpms (never did this before).

I have noticed that messing with the octane compensator on the dash raises the idle and makes it run a bit better however if I do this it idles WAY too high.

Fouled plugs lead me to believe it is running too rich.

Does anyone have any good places for me to start trouble shooting?

After spending so much money on the engine rebuilt I would like to enjoy the car. I am also hesitant to take it back to the mechanic that installed the engine because I feel I can trouble shoot and get it running better in my spare time.

[Frank Reiner]

Originally Posted by mabbonizio

Hi Folks,

I realize there are not many forum members with Adenauers but am hoping that someone who has worked on one, or just has a good knowledge of older cars with Solex carbs can chime in.

I recently had the motor in 1954 300B Cabriolet rebuilt. Prior to the rebuild the motor ran flawlessly, started immediately, but had a knock. After the rebuild the knock is gone and motor runs OK. It can be very hard to start when hot and usually requires me to press the accelerator to the floor.

It fires up just fine when cold but after a few seconds begins to stutter. The idle fluctuates from high to low and if revved will choke a bit.

If I tried to simply drive off the motor will bog down and cut out, however if I let it warm up a bit it will run and drive ok but idle rough. Additionally if I try to climb a hill in say 3rd gear at a low rpm the motor will bog down and cut out. It is VERY jerky at low rpms (never did this before).

I have noticed that messing with the octane compensator on the dash raises the idle and makes it run a bit better however if I do this it idles WAY too high.

Fouled plugs lead me to believe it is running too rich.

Does anyone have any good places for me to start trouble shooting?

After spending so much money on the engine rebuilt I would like to enjoy the car. I am also hesitant to take it back to the mechanic that installed the engine because I feel I can trouble shoot and get it running better in my spare time.

As a starting point, ensure that valve clearances, and compression pressures are correct, and that ignition timing is properly set. The octane selector adjusts ignition timing; that there is a noticeable change in idle speed with selector manipulation suggests that basic timing may be off.

The highlights are complementary.
Look to high float levels, and/or a leaking float valve in one or both carbs.
Does the carb package include a supplementary starting device, i.e., a standalone starting carb that is separate from the main carbs and the choke/enrichment devices that are a part of them?
Are the chokes opening as the engine warms?

[Benz Dr.]

Those chokes have a rotary valve plate and if it's not set in the correct quadrant will make for very rich running. From what I remember, the chokes are shut off by heat riser tubes coming from the exhaust manifold.