My 1983 300SD appears to have some electrical hiccup in the starter system.

Last Friday I turned the key an got nothing. About every third try I would hear the Solenoid click (At least I think it was the solenoid and not the GP relay.) After fiddling around a while I disconnected the neutral switch, inserted a jumper wire into the connector, and she started without a hitch. Problem solved I thought. Ordered a new switch from Fastlane, installed it... no start. Crap.
Cleaned the ground strap and all easily accesable connections... no start.
Asked loving wife to turn the key while I measured things with the voltmeter. She holds it down a couple seconds extra and it starts.
I drive the car to my regular mechanic and of course it starts EVERY time he trys to start it. He tests the starter "under load" and finds no problem. I come back and can't get it to start until the third turn of the key. Uggh. We both figure it is the evil, impossible to reproduce electrical gremlin.

The key switch was replaced two years ago. Alternator and battery are about six months old. The night before it refused to start I ran over a BIG (4' x 8') piece of cardboard. Hit hard enough to rip off the front license plate holder, that's why I first looked at the neutral switch. Part of the connector plug came off in my hand where the wires enter the plug, but no bare wires are exposed.

Sunday I plan to clean up the ground behind the instrument cluster and the key switch connections. If that doesn't work I might have to rig up a push button starter to the solenoid. Any other suggestions?

I still want to rule out the cracked NSS connector. Where can I bypass the neutral switch in the engine compartment? Other posts mention a three wire terminal block on the passenger fender well, but I have a four post block where two of the posts appear to share one common copper plate. Do I connect the other two posts to bypass the NSS?

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Greg Schwall

1983 300SD - 465,000 miles

If the noise is coming from the solenoid then you need to look at the starter. The solenoid can engage (click, clunk) and not turn the starter. This is not uncommon at all. Loose connections can also cause the problem. Make sure to check the connections on BOTH ends of all of those battery/starter cables.

PEH described the route which the electricity takes to get to the solinoid INSIDE THE STARTER.... a search would bring that up....
I had the same symptoms you mention.... the main contraption inside the starter which holds the brushes was not tightly held against the inside end of the starter housing. They showed me where the loose bolts had been arcing...
Replaced the starter , Bingo, starts instantly every time now.
I had already taken the chrome ring off my keyswitch in anticipation of having to replace that... but decided to try the starter because I really really hated to have to deal with the keyswitch.... and I got lucky.

had the same problem,

replaced starter
replaced solnoid
hardwired an external ford style solenoid

ulitmately the problem showed up ONLY when the engine compartment was hot after a long run.

even then, when I jumped it using a insulated piece of wire across the starter solenoid terminals ( no hair on my right forearm by being burnt off by the exhaust downtube) it would ALWAYS start.

Obviously it is some wire in the circuit (only possibility is the trigger from key switch) increasing resistance when hot

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1982 300SD (214 k, excellent shape) kidmobile running mostly biodiesel, gets 31 mpg hwy with 2.82 rear from a euro 500SEL



1976 115 body 240D 4-speed (traded for Jeep parts) - Engine lives on in my CJ7

U may have a L-R (door direction) play at the NSS.

Take a nylon tie and tie the NSS arm to the linkage next to it. That may solve ur problem

Had the same symptoms on the 220D back when it was the daily driver, and pretty much decided that it was poor contact at the solenoid. When all of the wire terminations and the bases at the threaded connectors had been polished, the problem seemed to go away for a while. However after a year or so it would come back. A good contact grease would likely have protected these contact areas from oxidation and the resulting poor (high) resistance in heated conditions.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150

You may also want to check your grounds. Start at the battery and take the two terminals off, clean them and the battery post and reinstall. Take the bolt loose where the ground wire connects to the body and make sure the wire and c onnection is clen and then install the bolt. Do the same with the ground connection between the body and engine.

Cleaned the starter connections, the starter ground, and the grounds behind the instrument cluster this weekend. Didn't see any obvious bad wires while I was working either.

Still not starting every fifth or sixth try. Since the keyswitch is only 2 years old, I guess I'll be ordering a new starter. I imagine the one I've got now is the 2nd or 3rd one this baby has seen.

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Greg Schwall

1983 300SD - 465,000 miles

So how many more things do you have to check before you accept my advise ? LOLOLOL

Oh maybe another dozen or so..

I don't mind replacing the starter, I just didn't want to go through the trouble and have it turn out not to be the problem. A loose brush holder would agree with the fact that this all started when my underbody got smacked with that road trash.

If it isn't the starter at least I'll have a spare on hand when I need one in a few years.

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Greg Schwall

1983 300SD - 465,000 miles

I did not actually say replace the starter... if you have taken any apart before you might just use ' electronic cleaner' on it... put grease back in the proper places, and tighten or replace those few little screws.. then if that does not work... you take it in for as a core... they don't expect starters brought in as cores to be working anyway... so they don't penalize you for trying to fix it...

It is common for starter motors to have one segment to have a high resistance connection. This does not affect it's operation much, unless it happens to stop with that segment as the one which will be energised first when the start is powered.

The temporary start fix is to hammer it a bit, until the rotor manages to turn a bit. Then it will turn over almost like new.
Every once in a while (5-10 operations) it will stop in THAT position again.
The fix - Replace it.

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Tony from West Oz.
Fatmobile 3 84 300D 295kkm Silver grey/Blue int. 2 tank WVO - Recipient of TurboDesel engine.
Josephine '82 300D 390kkm White/Palamino int.
Elizabeth '81 280E, sporting a '79 300D engine.
Lucille '87 W124 300D non-turbo 6 cylinder OM603, Pearl Grey with light grey interior


Various parts cars including 280E, 230C & 300D in various states of disassembly.

The hammer fix does not narrow down which of the faults exists... it may work on the loose brush holder also....

Got a "new" Bosch rebuild starter in. So far no problems starting.

Everything I read on the site says a 300SD needs the wheels turned to the left to remove the starter.
However, even with the stop removed and my wife turning all the way to the left, I was still a couple milimeters shy of wiggling it out. I finally managed to get it out with the wheels turned slightly to the right . It slid out right above the inner connector of the tie rod with the solenoid facing the floor and the bottom of the starter scraping the wheel well.

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Greg Schwall

1983 300SD - 465,000 miles

I think you are ' 'home free'.... FIXED !
On my 240d the starter comes out by bringing it straight up.
The advantage to not having that turbo in the way.... LOL