Have a 1985 300SD turbo,2998cc 6cyl.Cars been running fine,then i shut it off and now wont crank over at all.Batt is fully charged, all lights,gauges work.I crossed the starter soleniod and it cranks.Checked the wire from the switch on the soleniod and it has no current in crank position.Any help on
what to look at now would be great.Also i checked the wire conections under the air cleaner and no power on the switch wire.

Common problem on German cars of all stripes .

Just for grins , next time , try easing back on the key a little bit then turn it to start again , if you encounter the anti-starter lock you let up too far on the key ~ there's always a sweet spot in there .

Occasionally the plastic (electrical) portion of the key switch goes bad and must needs be replaced .

Sometimes the switch gets resistance and adding a simple relay to the starter circut on the inner fenderwell cures the problem permanently , this is true when it's a -hot- no crank problem .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I stopped at our county fair one nice day last August, and shut down my W123 Turbo 300 and when I came back a couple of hours later it would not crank. I got a pull start from my son and drove it home. I simply can't find why that circuit is dead. All the grounds are tight, transmission safety lockout switch with the back up lights working does not seem to be the problem, I replaced the switch from my parts car all to no avail. So after all the work I did, I still ended up getting a low cost push button switch from NAPA and mounted it very nicely to the left and slightly below the ignition switch and ran the two wires through the speedometer grommet, then behind the engine to the small circuit box with a cover on the passenger side of the engine compartment. Jumping the two small screws in that box will definetly crank it up. I don't like the fact that I have by passed the safety starting circuit, but nobody else drives my Mercedes and I can live with it. So I turn the key, glow and push the button. Nice in the fact that if it does stall at start up I didn't have to recycle the switch.

__________________
Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!

This may have absolutely no relevance but...

IF the car has an alarm system, and the alarm system was wired into
the starter circuit, you might have the symptoms you describe.

I drove a car for 11 years with a big red starter switch wired into the
dash. Switch went straight to the solenoid.
When I went to get it ready to sell I discovered the previous owners alarm system wired into the starter wire from the keyswitch to the firewall, right
under the steering column/dashboard.

None of my cars have add-on alarm systems now. Once bitten...

My W123 also had a nonfunctioning alarm system, which I removed some parts of shortly before my starting system failure. Matter of fact, I think it happened within a week of me pulling that junk - but not exactly the same time. Maybe a day or so later - why would it continue to start at all?

__________________
Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!