If it were my car I would do 3 things that are easy ways to check two basics-
First, if you can find someone to help, pull a spark plug connector at the plug and out say a screw driver or something in the end of it and position it close to the plug. What you are trying to do is to see if there is a spark. Do Not Hold the wire while you do this as the spark system has a lot of volts!
Second, while the right-rear door is open so you can hear it, turn the key on and then off again. Do you hear the fuel pump? You should be ideally in a quiet location maybe next to another car or a wall, or have someone listen near the right-rear wheel.
Third, take off the air cleaner cover. Turn the key on and gently move the air mass sensor plate. You should feel a resistance from fuel pressure and most likely hear it as the key goes on and off, pressurizing the fuel distributor.
The OPC could be the problem as well - or the MAS relay. Both are located on your car, I believe like my '91 behind the battery, behind a vertical black plastic splash shield. Push down on the top of it and then pull out. Revealed are the two relays.
The OPC has a fuse at the top of it. Remove the fuse (under a clear little plastic cap) and make sure it is good.
The MAS relay is the tall silver device that can only be removed by twisting its black knob at the top counter-clockwise. I have no way of testing it. I went to a junkyard, paid for a used one, had them put their mark on it in case I needed to return it. They agreed. Never returned it. It was the problem.
Finally, are you sure there is enough fuel in it. I have been down this road before and what started one car was a couple of gallons of fuel. You could have crap at the bottom of your tank or even a bad sending unit.
Keep us posted.
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)