I have an 84 300D. Sometimes, and without a pattern, it will fail to start. all electrics work, but when the iginition is turned on, nothing happens, or there will be a "click", then nothing.

I posted this before and it was suggested that the starter was overheating during longer drives, but sometimes it won't start fresh and cold. I'm pretty sure the positive battery cable was replaced about a year ago. The battery has a charge. I assumed if the starter was going, it would just go, not slowly die.

What am I missing? Please help me with this irksome problem, as this car is soon to be my daily driver again...

Could be a sticky starter solenoid. Try tapping the starter with a hammer when it fails to crank. It also could be a bad neutral safety switch. have you tried starting in N?

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

My thought is Ignition Switch, if you say all other starting/electrical systems are OK and it happens hot or cold intermittently.
May be someone else can chime in........

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FRED

Daily Driver: 98 E300TD 199K
Hobby Car: 69 Austin Mini
Past Diesels: 84 300SD, 312K
87 300SDL, 251K
94 Chev. K-1500 6.5Ltr.TD, 373K

Common problem in 123's usually attributed to dirty contacts in the ignition switch. My 85 TD does it every few months for a day, then goes back to normal. I carry a short piece of wire to jump terminals 1 and 3 in the small plastic box on top of the right fender in front of the battery when the problem happens.
Some people have added a solenoid on the firewall besides the battery to overcome the problem.

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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 vote for solenoid.

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

check the brushes?

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'81 300D - swapped to a 617.951 turbo motor with a 150 amp alt.

That is the hardest one to check and replace, so I would try the other options first.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

true but my roomates '77 datsun was doing the same thing so we pulled off the starter and completely took it apart, the brushes were just slivers that fell out very easily.

luckily for us it was a napa part and he has the only '77 B210 in the southeast so free one from its warranty.

so check those as a last resort.

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'81 300D - swapped to a 617.951 turbo motor with a 150 amp alt.

X2 next time it does it whack it with a broom and I bet it works. Time to order a rebuilt starter.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

The problem is either the ignition switch or the starter. But, rather than just hazard a guess..........where you've only got a 50-50 chance of success, I'd get some data first.

If you have a voltmeter, get the probe to the starter and hold it on the single wire that is attached to the solenoid. This is the 12V source from the ignition switch and commands the solenoid to close and apply power to the starter.

If you have 12V when you turn the key to "start" and nothing happens, the starter is the culprit. If you don't have 12V, the ignition switch is the culprit.

I'm making the assumption that you've already checked the basic tasks such as battery cable cleanliness on both the battery end and the starter end.............

I believe that if jumping 1 and 3 in the junction box on the top of the right fender activates the starter, then it shows the starter is good and problem is in wiring or ignition switch.

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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

Hey everybody Im new here. Just bought my first 85 300 D with the same problem. I tried the hammer on the starter with no luck, but kept bumping the key and finally got her to start

Try jumping the terminals as I described above next time.

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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 briefly scanned all of the other replies.....don't think that anyone mentioned the Engine Ground strap.......

Try hooking up a set of jumper cables......connect the negative terminal of the battery directly to the engine block......if she fires right up, you need a new ground......

SB

FYI......This is a common problem on older Autos.....a bad ground can have all sorts of effects from bad alternator symptoms to bad starter symptoms.....as well as all sorts of weird happenings on electronically fuel injected gassers......

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Diesels:
'85 300D, "Max, Blue Benz", 155K, 27.0 MPG
'84 190D 2.2, "Eva, Brown Benz", 142K, 40.2 MPG
'77 240D (parts car)
'67 Eicher ES 202 Tractor "Otto" (2cyl, Air Cooled, 30HP)
Gassers:
'94 Ford F-150, "Henry", 170K (300 Six) 17.5 MPG
'85 190E 2.3, 148K....Parts Car
'58 Dodge W300M Powerwagon (Flat Fenders) Less than 10 MPG

You've got That right!

Bad earth-straps can have some Very (!) interesting effects with things like Throttle-cables spontainously combusting!

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Alastair AKA H.C.II South Wales, U.K. based member

W123, 1985 300TD Wagon, 256K,
-Most recent M.B. purchase, Cost-a-plenty, Gulps BioDiesel extravagantly, and I love it like an old dog.

W114, 1975 280E Custard Yellow,
-Great above decks needs chassis welding--Really will do it this year....