Hello all.
I have just tested the duty cycle measurement of the fuel injection in my 190E 2.3 8valve (1992).
When measuring with an oscilloscope between pin 2 and 3 (gnd in pin 2), I see the following:

Car warm, when contact on but engine stopping, fixed duty cycle around 30% (not sure of this).
When starting the car, it climbs to about 50% until the car warms up a bit.
Then starts oscillating a little bit. At idle, around 40-45% (time that the signal is 0V compared to the total cycle).

If I rev up the engine until, say, 2000-3000 rpm, the reading then drops to about 25%, oscillating a little bit (20%-30% or so). That's consistent if I hold the speed.

The temp of the engine was about 80deg.

Is the car running too rich? What is the expected effects of this? Can I adjust it just by turning the 3mm allen to the left a little bit?

I would like to hear your opinions because I would like to adjust it by myself.

I can post some photos if you need them.

Thanks in advance,
Sergio

My understanding would be that the EHA is working with your readings. This would mean you are not running rich. If you were to adjust the mixture, you could only possibly improve running when in open loop, such as cold O2 sensor.

Are you trying to solve a particular problem?

Steve

__________________
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7

Those numbers look right to me.

Are you in Europe? On our our US cars, the mixture is 'tamper resistant' and the 3mm allen must be accessed before mixture can be adjusted.

__________________
'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

Thanks for your responses.
From several postings here, I believed that the duty cycle should be around 50% with slight variations both at idle and at higher revs.
I have no particular problem, only some rough idle, something even stalls and the feeling that my car lacks power. I know that this adjustment has been touched, so I only wanted to be sure that everything is ok.
The 25% duty cycle sounds quite low to me, are you sure that this is ok?

The duty cycle should drop when you give the car throttle (air).

Some people say the sweet spot is anywhere from 45% -70%. Play with it and see if you get any improvement. But if it were me I would solve that stalling problem first. When does it stall?

__________________
'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

It stalls sometimes when starting and exiting from my garage, for example, I have to press the throotle a bit to hold it up. After that, no problem usually.

If the "sweet point" is between 45 and 70%, and the duty cycle decreases as the throotle is opened, what r.p.m. speed should I check and what duty cycle should I look for?

Thanks