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Won't turn over

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Former Member
Greg's picture
Takoma Park, MD
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1994 E420
1986 420SEL

Going nuts with my '94 E420

Trying to fix the antenna this morning (no luck) and I notice something odd. First, the radio comes on, but nothing out the speakers and then I notice that the courtesy light won't go out. I fiddle around, start the car and note that the battery is a bit weak, start again, slow cranking, start again, just a click.

OK, charge the battery, still just a click. Found a bad fuse, replaced it. Swapped batteries with a known good one (from my other running Mercedes, same battery type). Still just a click. Then nothing, no click. The rest of the car's electric are working, lights, radio is now fine, (and even the damn antenna now). All the dash lights working, car ran fine yesterday. The bettery works fine in the other Mercedes. Checked all the fuses, even the ones in the base module. Disconnected and reconnected the battery, still won't turn over.

I'm going nuts, any suggestions? (PS I replaced the wiring harness about a year ago, so I don't think that's the problem).

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Former Member
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Takoma Park, MD
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1994 E420
1986 420SEL
Re: Won't turn over

Latest: With ignition on, air recirc light is blinking. Is it supposed to do that?

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Re: Won't turn over

Not fast and easy, but cheap. Remove, clean and reinstall both ends of both battery cables. Do the same with the braided cable going from the bell housing to the body.

Could also be the starter or the ignition switch or...............................something else. Section 24 of the W124 Service Library CD will provide the schematics you need for troubleshooting

Contact your GWS section and see if someone can loan you a copy of the Service Library.

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Virginia Beach VA

87 300SDL
95 E300D

Former Member
Greg's picture
Takoma Park, MD
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1986 420SEL
Re: Won't turn over

Cleaning the battery was step one. Getting at the starter on the V-8 is not at all obvious. I'm suspicious of the ignition switch and the usual culprits since it died slowly, then wouldn't come back.

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Former Member
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1986 420SEL
Re: Won't turn over

OK, crawling through the dirt (since the car won't move). There are two wires going into the back of the solenoid. The big one is hot. I'm assuming the little one sets the whole thing in motion. I connect the little one to hot, current flows, but nothing happens. I note that the little one is grounded (is that right?), but when I turn the starter it becomes hot.

Any opinions appreciated, but I'm guessing that the starter motor needs to be replaced, although I'm bothered by the fact that that little wire is grounded.

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Former Member
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1986 420SEL
Re: Won't turn over

Answering my own question: solenoid is a coil, so would have a direct connection to ground, right?

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Anonymous
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Re: Won't turn over

Yes. The starter case is grounded. The large stud drives the starter motor, the small stud engages the starter solenoid. Shorting the large stud to the small stud should cause the starter to engage. If not, you have either a bad starter or a bad wire connection. The wires are cheaper to check...

Yes, it could be the ignition switch, but what a pain to get at.

For the record, the wire to the small starter stud is called the "Circuit 50" wire, and it is universally purple.

Former Member
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1986 420SEL
Re: Won't turn over

Thanks!

Ran a hot wire to the small stud, nothing happened. Put a voltmeter on the wire leading to the large stud, it was hot. Put a voltmeter on the (disconnected) wire leading to the small stud and turned the key, got 12v.

Removed the starter (easier said than done). Using a 35 amp battery charger ran the negative to the case, positive to both studs (simultaneously), nothing. I'm assuming that it's the starter.

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Re: Won't turn over

One trick you might try is to pound on the starter with a big hammer while your assistant tries to start the car. If successful, replace the starter as the brushes are likely worn out and the rest of the parts are well on their way.

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Former Member
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Takoma Park, MD
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1994 E420
1986 420SEL
Re: Won't turn over

Tried that one (without the assistant), roughly on the spot that says "Don't hit with a hammer". Needless to say, nothing happened. I've ordered the starter from Rusty and will let everyone know how it turns out.

Greg

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Former Member
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1986 420SEL
Re: Won't turn over

Well, replaced the starter motor, that was the problem. But now I think I'm in limp home mode.

Does anyone know how do to get out of it (or how I got in it in the first place)?

Thanks -- Greg

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Re: Won't turn over

I may be wrong and your car may be limping home, but not in the limp home mode. The 2 transmission normally put in your car do not seem to have that feature. They are both 722.3XX transmissions. Can you describe the current performance of the car and when it started?

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Former Member
Greg's picture
Takoma Park, MD
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Joined: March 4th, 2004

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196

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1994 E420
1986 420SEL
Re: Won't turn over

Well, you were right, it was limping alright, but not home. I took it out for a test, lurching, stalling, very erratic. Then it stalled out. It would start, but then die right away. If I disconnected the battery, then reconnected it, it would go about 100 ft before dying again.

Got it home, (100 ft at a time) and hooked up my diagnostic tester (not that I have any idea what the codes mean) but it didn't light up (worked fine two days ago). So I disconnected the battery and checked out the fuses on the base module (the one closest to the fender) and discovered that the second fuse from the front of the car had blown (no, the fuse hadn't cracked, it was blown). Replaced the fuse and voila. Car runs fine.

This all happened after I was trying to fix the antenna, then the starter motor went and, with much cursing along the way, I replaced it. I used the diagnostic tester a few times, pulled few fuses to check them. Was careful to always disconnect the battery when fooling with the starter (I've got the radio code memorized now), no big sparks. Oh, the car was running fine before I started messing with the antenna.

I would really like to have some idea what was going on, any suggestions would be greatly appreciated.

Thanks! -- Greg

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