I have the same problem with my '85 190E 2.3. I posted the question and the reply I got said the engine would run but, that it would at least run more fuel. From what I understand without the OVP the computer is not able correct the fuel mixture and all that stuff. Mine was using alot of fuel and now is running real rough. I am going to try to find a relay this weekend. I will let you know if it corrects the problems.

Good Luck
Dan