http://www.landiss.com/mixture.htm

According to this article, the author's battery voltage is 13.6 and to get a baseline; ignition on, engine not running, voltage between pins 2 and 3 on the X11 connector, I got 3.78 volts. Where is he getting the 13.6V from?

At idle I get ~6.7V and at 2500rpm I get ~5.0V

Since the duty cycle % formula uses 13.6 volts, I'm wondering where he gets it from. He mentions 14.0V at battery. Very confusing. Can someone shed some light?

1988 300E M103 60K miles

The main reason of checking pins 2/3 with key on, ignition off is to check for faults. If you do not get 100% battery voltage reading, that 3.78V is indicating a fault somewhere. I'll try to dig up the fault list.

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http://i193.photobucket.com/albums/z...-RESIZED-1.jpg
1991 300E - 212K and rising fast...

John, it's my understanding that this so-called static test (KOEO, pins 2-3) is to establish which version of the computer is installed in the car, either the federal version registering 70% duty cycle or the California version registering 85%. When you plug the 3.78V the OP got in that test into the formula, that turns out to be almost dead-on 70%. That doesn't indicate a fault, that establishes the presence of a federal computer installed in his engine. His other test results with engine running also appear to be good values, although the voltage needs to be oscillating around 6.5V (or, in other words, around 50% duty cycle).

The 13.6V is battery (alternator) voltage when the engine is running.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

Right, I have the federal version. I used 13.6 in the formula but I have no idea where it's derived from. Pin 1 with the engine running? No mention in the article.

Oscillating around 6.5V @ idle or @ 2500 rpm? Thanks.

Will setting at 50% duty cycle (~6.5V) at idle still pass emission tests? Factory setting was leaner by about 1/8th turn (~5V).