240D Can't stop the smoke!

[mercmad6.3]

Check the coolant temp with a thermometer. Your thermostat could be stuck open.Nothing kills an engine like running too cold.

[Govert]

The second valve is a protection against backwards running of the engine. When the front valve opens, it should open the second one as well.



The first valve should indeed have a spring, so that it returns to the closed position if you release the accelerator pedal. Springs are available new.

The adjustment of the full-load screw is in the FSM of the Heckflosse, but not in the later ones as far as I can see. The full-load screw determines the maximum amount of diesel injected. It is screw 23 in the picture below:



Best to leave it alone at the moment, first the valves must work properly.

Compression is not the issue, always good to know.

The copper washer needs to be replaced every time, but I doubt that it causes the smoke. If you experience other strange effects, replace the washer. Get them from the dealer, they are not generic ones (best get a bunch of them).

Adjusting the poppet cam control rod is described in the FSM. Basically at idle the rod should be raised a little bit to connect.

The temperature is low, it should be above 80 degrees C. It could be the thermostat, but it could indeed also be the temperature sender. Check and replace thermostat/sender.

[billhard]

Here is what I found:

The inner throttle moves very little remaining nearly full open even at idle. See video here. I can move it freely by hand, is this correct?

I looked over almost every part of the "Diesel Injection System" portion of the service manual and find no reference to adjusting poppet valve. The poppet valve sits all the way down at idle, so I will move it up some, how much do you recommend?

I will order the spring for outer throttle next week along with new copper washers and temp sensing unit. I have recently replaced the thermostat with a new one so do not suspect that. Using an infrared thermometer the radiator is about 165F (74C) when at operating temp.

[mercmad6.3]

Still too cold. The engine needs to be between 80 and 90 C to run properly.
You may have a Summer thermostat installed. There are two types,one for winter and one for summer .
The reason you cannot find a lot of info is because the pumps are supposed to be tested on the test bench and once set should never be touched again.

[billhard]

Originally Posted by mercmad6.3

You may have a Summer thermostat installed. There are two types,one for winter and one for summer .

I can only find one temp available in North America, 80C. I have even looked on EPC, Mercedes own factory parts catalog. Could this be a regional thing?

Originally Posted by mercmad6.3

The reason you cannot find a lot of info is because the pumps are supposed to be tested on the test bench and once set should never be touched again.

While the poppet cam is internal, it is directly controlled by an external lever connected to the throttle linkages. To me this means it's adjustment could not be set without the IP mounted to the motor.

[Govert]

The second valve should indeed move freely, it looks good on your movie. It is only there to protect the engine against running backwards. Under normal conditions the second valve should always be as open as the first. You can see it is forced open by the movement of the first valve.

You are indeed missing a spring.

Look in section 30 Accelerator control for adjustment of the poppet cam control rod (and the other control rods).

The 80ºC thermostat is the correct one and the normal operation temperature is indeed 80º–90ºC. The temperature in the radiator might be lower because of the cooling. Perhaps you can direct the infrared thermometer on the engine to be sure.

In the old days summer and winter thermostats were normal, but it is not necessary.