I have been working thru my 1990 190e for a while, and was about ready to smog it this week.
Yesterday, I checked, but did not touch the Duty cycle, and it was cycling around 40 to 50%, and the car was running really sweet, and smooth.
I decided to check the voltages at the O2 sensor, and back probed them with my DMM... I was not sure what reading I should be getting, so came in to read up, leaving the car running to warm up.

When I came out, I noticed that the engine sounded a little lumpy.
I goosed the throttle to see if it cleared it, and the engine spluttered and refused to rev.... soon after that it stalled.

Every time I tried to start it after that, it would start and run for a few seconds and then stall.

I left it overnight.
Today, it wont start.
I put a gallon of fuel in, as the tank was getting near empty,still no start.
I checked the fuse in the OVP, and it was good... The OVP looks old and rattles when shaken.
There is a visible spark at the sparkplugs.
There is fuel pressure at the upper chamber of the FD...

Ideas?

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2009 Mercedes ML320 Bluetec