300SD has starting issues
 

My dad is out of town, and I was supposed to use the 300SD to get some things done to it at the shop. well, I had to come back home for a few mins, and when I went back out to the car, I could not get it to start. I did the usual, I put the shifter in both neutral AND park before each time I tried to start it, no starting. The car has been doing this for a good long while now, and then I remembered what he told me to do if I was ever driving it and that would happen. The mechanic gave him a piece of wire, and told him when it wouldn't start, to put the key into the preglow position, to open the hood, and touch these two outside screws in a row of four located in a plastic rectangular box on the passenger's side with the wire, and the car would start. Well, I don't like doing that, it seems dangerous, and I need to know what the real problem is. I'm thinking it's the starter, but for all I know, it could be something cheap.
Thanks,
-Joe

since you have needed to fool with the shift lever position for some time to get it to start, I would suspect the neutral starting switch. This switch, just aft of the modulator on the left side of the trans, inhibits current to the starter solenoid unless it senses that trans is in neutral or park.

Very likely its the neutral sensing switch on the tranny BUT I had a problem similar to yours, I didn't mind using the short piece of wire to hot start the car (it was VERY intermittent!)
But my wife uses the car occasionally and she is not capable of doing that so I replaced the neut switch. Then, Lo and Behold! the problem still was there :(

It has since been determined that my starter switch (so-called ignition sw) is probably the culprit, so don't rule that out too as potential source of this kind of problem.
It isn't your starter, after all the car will start OK when you use the jumper wire, doesn't it? so its not the starter motor!

Is replacing the starter switch an easy DIY project? Is the starter switch considered to be a cheap part?
-Joe

I had the same problem, still do. I put the magic red button under the dash, hooked the button to a Bosch relay and the Bosch relay to the two screws mentioned earlier. The wife was driving the Benz and it stuck her in Austin one night. The next day the button got installed.

Shifter bushings possibly?
 

Another option is shifter bushings. If there is enough wear, it may not be moving the arm enough. www.**************.com sells a kit with bushings and a little tool for installation.

If this the case, it would be advisable to get into the habit of using the parking brake or it may not be in the same place you left it. :eek:

I posted before that there is nothing wrong with the shifter. It's not rattling or sloppy like my 300D used to me, its shifter is quite firm. I think that it's the starter switch. They don't cost too much, but I don't know how easy the job is for the beginning DIY'er.
-Joe