If it's a stock 190D or 200D fintail it doesn't even have a relay for glow plugs. You have to hold the start knob out just to the point of resistance where the alternator (generator?) indicator light dims slightly but the starter is not activated. If the glow plugs work, you'll see a glowing filament in the round "salt-shaker" thing to the left of your steering wheel (that's your glow plug light!). If this doesn't glow, either your pull start switch is bad (you can by a new one at **************.com) or one of the series glow plugs has failed, so the whole circuit is dead. The only reason I know this is that both these problems had happened to the 240D I was originally going to buy.

Of course if the car has been upgraded to the new design plugs it should have an aftermarket relay installed. The new plugs would have parallel wiring, so there are no metal "W" shaped things between the plugs but insulated wires instead.

Good luck restoring your fintail...they are eye-catching cars!

-AC
'76 240D "Katja"