That plug you have is only for diagostic testing at the dealer. you have no tach amp that plugs into it. just a cap to keep dirt out of the connectors.

Behind the passenger floor kick panel on the wall, is a black box computer thing. large cable connector with a bunch of wires going into it. EGR, rack position sensor, tack pick up etc... send signals to it. not sure what else it does.
The tack pick up is off the flywheel, on the drivers side. look down behind the oilfilter housing, there should be a plug with a small bolt holding it into the engine adaptor plate. has a large black cable attached to it. could be a broken connection there at the plug. above the valve cover on the firewall is a large round connector it plugs into. from there it runs through the firewall to the black computer box.

there is also the OVP (over voltage protection) relay, it is a silver box with a red spade fuse in the top. it could be bad. I think it is under the dash behind the glove box.

http://www.allpartsexpress.com/ShopByVehicle.epc?q=1985-MERCEDES--BENZ-300dt--/--L5--998cc--3.0l--Diesel--Fi--Turbo-Electrical&yearid=1985%40%401985&makeid=MERCEDES+BENZ%40%40MERCEDES+BENZ%40%40X&engineid=1193790%40%40300DT++%2F+L5%2D2998cc+3%2E0L+DIESEL+FI++Turbo%40%40300DT&catid=Electrical%40%40Electrical&subcatid=Overload+Protection+Relay@@Overload+Protection+Relay&mode=PA
http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1985@@1985&makeid=63@@MERCEDES+BENZ@@X&modelid=6193%3AMBC%7C1504%3AED%7C10000135@@300D&catid=241959@@Body+Electrical&subcatid=242058@@RPM+Sensor&applicationid=W0133-1615020&mode=PA

Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works