I have a 1986 300 E M103 engine and it occasionally has this problem where it starts and then stalls. Additionally the RPM gauge does not work until the engine is heated up or after about a min or two of driving. I initially replaced the injectors and that solved the problem temporarily. Then I replaced the Fuel pump. I also replaced the Voltage regulator. Out of all the times this has happened it has been raining outside or very moist I am pretty sure there is a correlation between the two. I just ordered an OVP Relay I have tested the old one and it works but there is corrosion on it. The 10 V fuse is good. I am stuck on this problem and I dont want to be left on the side of the road anymore. Anyone have any ideas?

 

OVP should have been the 1st thing to replace. If corroded, spray some WD-40 on it until you get your new one.