Is there a way to check the duty cycle using voltage readings?? I read this article BOSCH KE3-JETRONIC MIXTURE ADJUSTMENT and followed the formula:
reading from pin 2 & 3 on x11 connector divided by battery voltage and then 1-the sum of that and convert it to a percentage. So this is what I got:

my reading from x11 was jumping between 6.5v - 5.Xv
my battery voltage at idle was 14.4v
I divided 6.5/14.4 = .451
then I subtracted 1 - .451 = .549 which gives me roughly 55% + or -

Is this correct? Can anyone tell me what the normal duty cycle for my car should be roughly?
1990 190E 2.6 California versioin
It idles around 700-750 rpm which is what it says on my yellow sticker on the radiator bracket.

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1990 190E 3.0L

My 190E 3.0 is set around 40-45% I believe.

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I thought 50% was the target number?

I'm not even sure. I've been reading things that are giving me different answers. I have a California car and I heard they have a different % than other cars.

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1990 190E 3.0L

The Landiss article is excellent and specifies the proper range of duty cycles for 2500 and idle. I'm not sure if your duty cycle calculation is correct. It's best to use a meter that reads duty cycle directly to be sure. I borrowed one from a friend that has that function, and I recall there have been some threads on commonly available multimeters with a duty cycle function and one was available at a reasonable price from Sears.

Duke

A dwell meter, as found in many multimeters, may be used to check the duty cycle. Set the dwell meter to the four cylinder scale; 90 degrees = 100%, 45 deg. = 50%, etc.

Ismalley. 55% is fine. The closer to 50% it gets is the optimum, but anything between 40-70% seems to have no effect at all from my testing. Several factors will easily affect the reading by 5-10%, temperature being the major contributor. But,,, the numbers at idle and 2500 RPM should be within 20% of each under when at normal operating temp. I didn't test your formula - the actual duty cycle as MB measures it is opposite to normal convention; but if it's 45%, that's fine too. As stated above an inexpensive Sears multi-meter 382139 can be used to accurately read the DC. Just be sure to plug the RED wire in the gnd pin #2 on the round terminal - exactly opposite of what one would think.

DG