This problem is happening more often. 1984 300SD, sometime the key only goes - Click.

I then pop the hood and jumper the positive battery post to the white wires in the small black junction box on low on the passenger fender. It has a lid and 3 terminals. The motor will turn slightly, then the key works normally.

Where is the actual problem? The keyswitch or the starter solenoid?

Something else?

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1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI

Try connecting a remote starter across these points and if the started works then I would say its the switch. I replaced the switch on my car and it was not a bad project.

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1983 300SD
200000miles

Use a test light looking for +12 volts at the starter solenoid control signal when the key is turned. If the problem is intermittent, you can wire a small bulb or 12V LED in parallel with that control signal, place the bulb just under the rear edge of the hood. That way you can see if the solenoid gets the control signal each time you turn the key to START.


Could be something with the key, ignition switch, wiring, connections and/or could be starter brushes worn, solenoid contacts, sticky solenoid. The operation of the solenoid makes the power connection for the starter rather than a separate relay in series like in Many American cars and trucks

Look at my how a starter works thread.

http://www.peachparts.com/shopforum/diesel-discussion/369793-om617-flywheel-missing-teeth-cause.html

Have you checked it not just a tired battery or bad earth first?

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UK spec Mercedes W210 E300 Turbodiesel wagon - OM606.962 with 722.6 transmission - rust free!

Neutral Start Switch?

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83 SD

84 CD

Thanks for the advice.

When it cranks it starts easily.

When I jump the starter, I apply the power very briefly, it turns the motor only slightly. Then the key will start it.

I'm away to SoCal on a roadtrip, so its a good time to buy parts but a bad time to fix it.

I am leaning towards the sticky solenoid, because all of it does work as a system. The jump point must be slamming extra amps to the solenoid, making it engage.

When there is the problem, there is always a light click when the key is turned, so the keyswitch seems to be doing its job.

__________________
.
1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI

What are the two points?

I have been jumping the point on the left to the +batt terminal.

__________________
.
1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI

Jump it to the other screw with the red marking. You can use wire, a remote starter switch or even plier handles.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.

I would have to look but it's probably the same thing just that my way is using the circuit in the car. I have had two starters that had dead spots on the armature that wouldn't react so I had to bump them to rotate them a little then they worked.

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1983 300SD
200000miles

Next time it happens, leave the car in gear and rock it back and forth to move the starter off a dead spot. If it starts then you probably have a flat spot on the armature. (At least that is what I remember from American cars in the '60's.) If it is the solenoid, you will just get a series of clicking sounds.

Guys, correct me it this is not right.

Sorry! But you might be correct about the starter armature issue BUT; moving the crankshaft and the flywheel attached to it by rotating the wheels while the tranny is in gear will accomplish nothing with regard to the starter! The starter's drive gear is only engaged with the flywheel when it's energized, so there would be no physical connection that would effect some rotation of the starter armature itself.

If the solenoid is sticky using the key, why does jumping it make it engage?

__________________
.
1st MBz: 1982 300SD
2nd MBz: 1987 300SDL
3rd MBz: 1995 S420
4th MBz: 1987 190DT
5th MBz: 1984 300SD w/1983 300DT engine
6th MBz: 1999 C230k I'm 3rd owner, got it w/57,235 miles.
and manages Mom's 2007 R320 CDI

Maybe you have a sticky solenoid AND a screwy key/ignition switch!

Or maybe the ignition switch or the wiring to the junction where you are jumpering to is faulty, but when you make a good connection jumpering directly to the electrical junction it's a better connection.

But this is all speculation, what needs to happen is some empirical data has to be generated so that the various possibilities can be eliminated.

The other question that arises is why does the starter only move slightly when you jumper it directly? You should be able to just as easily start the car meaning getting the starter to engage and turn the engine over just as readily from that electrical junction as with the key switch.

Next time it happens try hitting the starter with a bar or hammer, wrench see if that gets it to engage might help you determine if you have a dead spot in starter.