Hello,

I have a 76' W115/ OM617 300D.

After trips over 30 miles or so, the car doesn't start back up once it's been turned off. When I turn the key, absolutely nothing happens. I don't even hear a click. When the problem is occurring, I can get the car started by using a screw driver to complete the circuit between the two large terminals on the solenoid. I usually just need to arc it and then I can get in and start the car with the key. A couple of times, I've had to complete the circuit and start the car with the screwdriver, but that's only happened about 1/10 of the time.

My starter seems strong and the solenoid works fine when the car has sat overnight or after short trips. Like I said, when I turn the key after a long trip, I don't even hear a click.

Does this seem like a solenoid issue? Or could it be wiring? Maybe the sensor that senses when the car is in gear? what is that called anyway? What would be the best steps to take to troubleshoot?

I don't mind buying a new starter/ solenoid, but if it's something I can fix for a few bucks, that would be preferred.

Any help is appreciated!

Thanks!

First inspect and clean the battery cables. Remove the cables from the battery and sand the contact surfaces of the connectors to a shine. Clean and lightly coat with grease. Then move on to a thorough wiring inspection. Look for oxidation, chafed insulation, bad crimps, loose connectors, signs of wear, etc. If the solenoid can be serviced, try to clean the contacts. If you have some multimeter experience, check voltages at all of the points along the way to the starter and for low reistance grounds.

Could be the neutral safety switch. Try starting it in neutral and not park. 123's are known for getting dirty connections in the starter switch in the ignition causing very similar symptoms. Don't know if the 115's have the same issue. There's a thread on here somewhere by a guy who cleaned his starter ignition switch connections and solved the problem. Some people have put additional solenoids in the system with the ignition circuit to deliver more current to the starter solenoid. Pictures of that on here somewhere too.
Lots of 123's have a junction box in front of the battery on the inner fender. Jumping terminals 1 and 3 in that box with a short wire will energize the starter and avoid having to reach down into the starter solenoid region. don't know if 115's have that junction box. I suspect they might because 116's had it.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I've had this issue come up in another car. It started fine when cold and wouldn't restart when hot.

It turned out to be a loose ground wire at the starter.

As mentioned above, look at the obvious wiring issues and treat as necessary.

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1974 240D "Boldie" 170K.- New timing chain/freshly rebuilt IP/replaced valve seals/injectors/upgraded stereo/new Bilsteins with Yokohamas/fresh paint and rocker panels plus lots of welds.

I concur with the above. I too have had similar issues when hot starting. It was loose starter wires.
Also try moving through the gears or starting in park. If this allows it to start then it's the neutral safety switch.

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Wow - thanks for all the advice guys!! It does sound like a wiring issue, but before I go through all of that, I will drive it awhile and recreate the issue and see if starting in neutral or other gears makes it work. If that's not the cause, I will get under the car this weekend and go through all of the wiring.