Check the sensor values...
Approx 900 ohms ..you are looking for .5v. at cranking speed.
if the sensor is working, the flywheel may not be indexed correctly [ which means you will still have spark, but not at compression stroke]

He may aslo have sent you a flywheel from a 16 valve engine[ 102.983].. they used the front sensor only. You have a 102.985.

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1M30LAGSC1TC0NTXVR&year=1987&make=MB&model=190-E-004&category=F&part=Reference+Sensor

http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1M30LAGSC1TC0NWHYW&year=1987&make=MB&model=190-E-003&category=F&part=Reference+Sensor

Again , test the sensors ohms value and cranking output.. that will tell you if it has a good coil [ ohms] and if the flywheel is triggering it [ volts ]................