Recently after a long trip, my 1979 300D would not start. I would turn the key to the "run" position and all the lights would come on as normal. After waiting for the glow plug light to go out, I turned to "start" but nothing happens. And by nothing, I mean NOTHING. The lights on the dash stay lit and the radio still plays.

I installed a new battery 2 months before this occured, so I don't think the battery is the culprit.

Thinking that the ignition switch itself may be the culprit, I whipped out the Haynes manual and have attempted (unsuccessfully) to remove the switch. After unplugging the connection to the back of the switch, I noticed a reddish goo on one of the plugs. I can take some pictures and put them on a website if necessary.

The first question is obvious: What is the red goo and could it be the cause of my problems (by blocking the circuit)?

The second question is: How do I remove the entire ignition switch? Once again, I can post pictures to indicate my current progress if necessary (in the Haynes manual, I'm stuck on Chapter 10, section 14, step 9). Namely, where is the steering lock clamp bolt, and do I have to completely remove the locking cylinder?

Thanks for any assistance.

No start? I assume from what you wrote that the engine did not crank or turn over??
If the starter is not engaging it could be the starter, but first just turn the key on, apply the parking brake, put the transmission in reverse, and check the backup lamps. If not on you could have a bad neutral safety switch on the transmission.
The next step would be to find to jump the starter to see if it will run. There is a connector on the frame next to air filter. Jump the correct two wires and the starter should crank.

Good luck...

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Ijust had a similar problem with my 1985 380 SE and it was a starter problem. I also thought at first that this is an ignintion switch problem. Let us know what was wrong.

MikeB

Sounds more like a starter problem than a switch. We rarely have to replace ignition switches. Use a volt meter and check for voltage at the start terminal on the starter solenoid. If you have voltage there, the starter or solenoid is at fault. Being that the starter is so close to the exhaust manifold over time the heat really cooks the starter. BTW, the red goop is most likely dilectric grease used to lubricate the switch and over time it starts to seep out of the switch.

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ASE Master Technician, Lead Technician for Deutsch American Inc. Over 6 years of Import experience-specializing in German Automobiles.

Metricman - I put the dashboard back together a few days ago when I realized I was in a bit over my head and tried your trick. Sure enough, the reverse lights did not come on (with the ignition on and the car in reverse).

I have yet to try the wire trick though, as I am wary of messing with anything electronic. Thanks for the help!

You would be messing with something Electric. Not Electronic. The small wire that is in the junction block for the alt. and starter will make the starter engage if power is fed to it.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM