Starter trouble???

My 1983 mercedes 300sd wont start and its driving me nuts. When I turn the Key I get nothing. I have replaced the neutral safety switch , the starter
and the battery all in the past year, so I dont think any of those are the problem. I tried something my shop teacher once told me, I turn on the ignition, and put a wrench across the posts on the starter and it started right up (after a few sparks). The problem was sudden and unexpected, so I was wondering if maybe it was the ignition switch? Does anyone have any tips on a diagnosis?
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can't for the life of me understand why your starter would start when you are in effect shorting it...... you have zero volts across it. I'll be interested to hear from others.
Have you measure the voltage across the starter, ignition etc?
cheers

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Starter always have power going there... that big cable is direct from battery. So by shorting battery positive to the selenoid trigger, it will start the car up.
This is easier done by doing it in the engine compartment...Just below the coolant reservoir... there is a row of electrical wire... The purple wire is the trigger wire for the starter so you can use a remote starter switch from battery positive to the purplr wire.
You should also get a 12V from that purple wire to ground when the igntion is in Start position... so have someone hold it there while you measure the voltagte.
It is possible and I think it is in your case that the ignition switch is faulty.
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    sure, of course, wasn't thinking. However, can I add what might be useful. Tried to repair the solenoid switch some years ago myself by buying a repair kit.... although the starter/solenoid worked perfectly on the test bench after the repair, it would simply not work in the car and after much fuzzing, I ended up simply replacing the whole starter.... suggest you do the same
cheers    
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Tiger wrote:

I tried your trick, and it worked, would that lead you to believe that my ignition switch was bad? When you say "switch", do you mean the actual key, or the switch behind it?
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What is the mileage on your car?
With remote starter, if you were able to start your car every single time, then I do not suspect the starter issue.
Have you checked the overload relay? In your fusebox... it is the only relay you have with red fuse on the top. Is the fuse good? Tap it around a bit with the relay out of the socket and reinsert. What is the date stamped on the side of the relay?
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If you hit the solenoid with a hammer does the starter work again (for a short time)?
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me wrote:

YES!! I tried hitting it, and it started, however 20 minutes later it would not and when I hit it again it wouldnt start. The starter is only 3 months old!!
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In my experience, probably a bad solenoid. Next time try hitting the solenoid (that appendage on the side of the starter when the battery is connected).
Removing the starter is not too bad, but it is *heavy* be ready for it when it comes loose. On my 300SD (95), the solenoid was replicable without replacing the starter, but the starter needed to be out of the car to replace the solenoid.
BTW if you choose to replace the starter or solenoid yourself, make sure you have the correct sequence of washers, lock washers and battery cable, and torque it correctly otherwise the battery cable vibrates loose and causes a poor connection. (this happened to me).
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Sorry. My 300SD was an '85. I lost ten years somewhere.

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With this new information, which I didn't see, it is your starter that is bad... very common to get some bad starter.
Where did you buy the starter? Remanufactured? Exchange it for another one. No way around this.
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