The mixture adjustment procedure in this thread was posted in the R129 forum and found to be unworkable for all U.S. cars. It's
my guess that as written it won't work for any vehicle powered by the M104 or M119 engine, and that includes some W124 cars. The problem is a fundamental error that makes it impossible to complete the checks which are designed to ensure the accuracy of the duty cycle measurements.
The information in this new post is based upon Mercedes' Startekinfo.com website and may not apply to all cars with M104 and M119 engines.
In case of the KE-Jetronic the duty cycle value refers to the square wave voltage’s ‘off’-time.
"Off" refers to low voltage, and that is the convention upon which Mercedes' documentation is based. A way to distinguish whether a duty cycle reading references the signal's time at low voltage or high voltage is to take a measurement with the key on, the engine off, and a coolant temperature below 70 degrees Celsius. Along this line post #2 states:
With ignition switched on (engine not running) the duty cycle should be about 70% (California: 85%).
According to Mercedes the duty cycle with a cool engine should be
30%, not 70% -- this fact may be inferred from reading
this table. To be clear, closed-throttle duty cycle is 70% for most W124s but is 30% for most if not all cars with M104 or M119 engines.
If a meter displays 70% its reference is wrong, and a simple remedy may be to swap the meter's leads to give a reading of 30%. Otherwise it is necessary to adapt to the incorrect reference by subtracting 100% from all duty cycle readings and then regard the negative result as a positive number. If a duty cycle other than 30 or 70 is displayed by a meter, then the throttle switch or other input is in the wrong state.
With ignition switched on (engine not running) the duty cycle should be about 70% (California: 85%).
If you’re using a voltmeter it should read 0.3 * Vp6 (California: 0.15 * Vp6).
If the duty cycle should be 30%, than a voltmeter should read .7 * Vp6.
A static (not fluctuating) duty cycle value with the engine running and the o2-sensor at operating temperature, indicates a problem according to the following list...
The list in post #2 is slightly inaccurate for an M119 or M104 engine. A more accurate and detailed reference which includes steps to troubleshoot the problem is found
here at Startekinfo.
A closing comment:
A duty cycle at idle fluctuating around a mean value of about 47% or a little lower is usually a good choice for an intact KE-Jetronic in my experience.
Steve Brotherton is an engineer with perhaps more experience with Bosch Jetronic injection than anyone on the planet. Over on Peachparts.com he states that his personal preference is to adjust the mixture rich for a 40% duty cycle.