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On STAR TekInfo there are documents providing engine "Test and Adjustment Data", and the one for variants of the M104 is attached. Its specification for "on-off ratio" (duty cycle) for a cold engine with throttle closed is 30%. Similar documents for the M119 and a variant of the M102 (M102.985) also specify 30%. Documents for all other listed engines specify 70% or 85% (California version).

So, for a W124 Mercedes specify closed-throttle duty cycle values of 30%, 70% and 85% -- the applicable specification depends on the particular vehicle and may not be known to the owner. However, all vehicles give an engine-off wide-open-throttle duty cycle of 20%, so I suggest this be used as a check to ensure that duty cycle measurements have the correct "glass empty" reference used by Mercedes.
 

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Discussion Starter #22
I want to announce that I discontinue my participation in this thread. Instead of explaning why, I refer to this thread in the 129 forum: http://www.benzworld.org/forums/r129-sl-class/2722145-ke-jetronic-lambda-control-duty-cycle.html … (read up from post #26). … In post #31 of that thread is another link for further clarification.

In case of doubts about the validity of the content of my posts here in this thread … it‘s well thought out and based on experiences with the engines in question here from the beginning. As a young design engineer I was personally involved in them before they came off the production lines.

For further information I can still be contacted via PM. … :)

H.D.
 

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I want to announce that I discontinue my participation in this thread. Instead of explaning why, I refer to this thread in the 129 forum: http://www.benzworld.org/forums/r129-sl-class/2722145-ke-jetronic-lambda-control-duty-cycle.html … (read up from post #26). … In post #31 of that thread is another link for further clarification.

In case of doubts about the validity of the content of my posts here in this thread … it‘s well thought out and based on experiences with the engines in question here from the beginning. As a young design engineer I was personally involved in them before they came off the production lines.

For further information I can still be contacted via PM. … :)

H.D.
VERY sorry to read that. I urge you to take the high road and simply ignore the ignorant poster.

The irony is that Georgia (Atlanta) was at the heart of the Confederate States of America. Talk about the pot calling the kettle black.

https://en.wikipedia.org/wiki/The_pot_calling_the_kettle_black
 

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I urge you to take the high road and simply ignore the ignorant poster.
Benzworld is a discussion forum where members freely exchange thoughts and ideas within the constraints of its rules. If a member repeatedly violated this spirit and attempted to dictate to you where you could post, would you not think they were acting in a manner reminiscent of Hitler/Stalin/Trump (take your pick)? If not, then this Pennsylvania Yankee suggests you shorten your username to "Lost".

In case of doubts about the validity of the content of my posts here in this thread …
...Look no further than the attached screenshot.

Presently there is not one single resource -- a Benzworld post, a YouTube video, a web article -- that correctly explains the mixture adjustment procedure for all M119 or M104 engines. If you fix the problems with your posts here and on the R129 forum that need will be addressed.
 

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"Pull off the vacuum line between the throttle valve and the regeneration valve of the fuel evaporation system at the regeneration valve and block it."


Anyone got a picture of where this vacuum line is?
 

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I'm confused by all this.

A lot of info, but hardly clear at all.

E.g. "Remove the plug from the adjustment tower (if it’s still in there)...."

How? Had to search other threads that you gotta basically hack the top of it to remove that ball bearing. What a stupid design by MB.


And still not clear for M104 engines. At idle, should it be 30% or 70%?


And: "With the throttle fully opened and the air sensor plate not deflected..."

Stupid question, but what is the air sensor plate?

These instructions seem a lot more clear to me: Beer, Bolts, Volts, and Bits: KE Jetronic Fuel Mixture Adjustment
 

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There are various ways to remove that steel ball in the tower. I've read quite a few different approaches. The dealer must have done it in my white TE and this new-to-me TE had it already done by someone. I know that in my parts box is a small tower with a gasket, new. I don't remember how or why I acquired that. It would seem to me if the tower unscrews that easily, the attack would best be performed off the car.

In any event, a lot of people confuse how Mercedes chose to do the duty cycle, i.e., the percentage of the cycle they used during the pulse period. Even people buying duty cycle meters get confused at what they are looking at. I just use a big analog meter on volts, hooked up to #2 and #3. I figured out what my cycle voltage was (with a digital VOM) and did the formula. My voltage is 13.7 found between #2 and #6, if memory serves me correctly (that voltage never seems to change). I take the voltage I found between #2 & #3 (which averages 7 volts) and divide that by 13.7.....I get .51094891. Then for percentage, I do this; 1.0-.51094891=49%

Ideally, my needle will swing from 6.5 to 7.5 with 7 volts as the median average. When your needle swings like this, it indicates your O2 sensor is at least working. Cars with well worn AF potentiometers will not be able to hold your adjusted duty cycle reading for very long. These instruction are for the M103.

Kevin
 

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my m103, someone had cut a slot on the side of the tower just below the balls 'equator', probably using a dremel cutoff disk or similar... this apparently allowed the ball/plug to be popped out, maybe with a small flat screwdriver?

the tower can't easily be unscrewed as it uses special screws with one way slots and breakaway heads.


the air sensor plate is the disk in the airflow meter that depresses with airflow... its directly above the throttle body. you can see it here ...

 

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I haven't examined the in-car screws, as the ones with the extra tower are just Allens. I've seen the procedure with the cut on one side written up and it is, yes, to pry the ball up. Glad this was done before me on both TE's.

My original white TE screw adjustment was always rough....IOW, it was not smooth to turn-easy to do either too much or too little while adjusting. I sprayed some oil down there and it had no effect. This new-to-me TE is a little smoother, but it's a lot younger in miles.....

Kevin
 

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"Connect the meter to the diagnostic coupling X11 port 3 and 2 (or ground)."


I get 100% w/that on my 90 300CE M104.980.

I get 80% w/the red in #1, and black in #3. Is that right?

And if so, is it really the "air intake temperature sensor"???

 

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100%: problem with the meter
or diagnostic coupling (X11)
or ECU ‘N3’ (missing connection to voltage supply or to ground)
or OVP (overvoltage protection relay)
or o2 sensor signal (short to ground)
or too lean setting (beyond the EHA’s ‘enriching limit’)


New OVP, new O2 sensor...

How does one test the ECU 'N3'?

If I turn the DC clockwise, car runs very rough and then can't start. DC % doesn't change regardless.
 

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Make sure your meter is measuring Duty Cycle not Hertz. Coincidentally the freq. of the signal is 100 (Hz).

Measure the actual voltage on the same pins in DC mode (not AC) as a sanity check. And report on:

(1) What is the frequency
(2) What is the duty cycle
(3) What is the DC voltage

Don't make any adjustments between these 3 measurements.
 

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Hi Robert.

Not sure if those measurements are consistent.

You should get a 100Hz signal as far as I know for all model years.
The 2.71 volt would be a duty cycle in the range of 80% (100% - 2.71V/~13.5V) ~ 80%.
But your meter is saying 170Hz and 100% duty cycle.

So something is strange.

What year is the manufacture year again?
 

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I'm not as familiar with the M104 engine, but those readings are still inconsistent (Voltage and duty cycle). At this point I would trust the voltage more than the duty cycle.
Use the average voltage method. Duty cycle = 100% - (Vdc / Vsystem) *100
 

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BTW, you can also use your Engine Analyzer "dwell" meter in the 4-cyl mode to do another sanity check. That is if you have one.

And the dwell meter will give you the Mercedes definition duty cycle (because it measures the percent time the points are closed for the old style adjustable mechanical points, which is similar to the amount of time the diagnostic port signal is zero from the X11 - mercedes definition)
 
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