Start and Idle/Vibration problem. 300E (124)
 

I am amazed at what I learn here. I have had a problem for quite a while with hard start, rough idle, and vibrations at low RPM. I have even rigged a bypass on my cold start valve to assist cold starting. While reviewing posts, I ran across a mention of the OVP (Over Voltage Protector). The description seemed to be close to the problems I have. I did a search on OVP and reviewed other post and saw many cases that were similar to mine. I went right home and found my OVP (which I never knew existed) and low and behold, the fuse was blown. I replaced the fuse and I now have good starts, idle and a lot less vibration. What a cheap repair! all that for a fifty cent fuse. :D Another area I was concearned with was very low to no oil pressure at idle and fluctuating oil pressure at 2 to 3K RPM. Again the post suggested replacing the sending unit. That worked also. Pressure now holds a 1+ bar at idle with no fluctuations at speeds. ;). Thanks to all!

I have the identical problem. Where is this OVP?? :)

Behind the battery. Pull off the black plastic cover over the computer and relays.