250SL Starter Motor Diagnosis Help Needed

[250SLFranco]

My 250SL won't turn over when the ignition is turned on.  I get the fuel pump noise and all electrical is functional, battery is fully charged but no turn over.  Responds very similar to trying to start when it is not in "Park" or "Neutral".  I know a proper diagnosis discussion is somewhere, but I am reaching out for help finding it.  I am trying to determine if I go directly to replacing the starter motor or if there is are considerations in between.
Thank you in advance for your input.....members have always been helpful!

[Jonny B]

Automatic or manual? Have you done any changes with the gearshift linkage? Did you try to start in another gear position?

[badali]

I replaced my starter last year.  Initially it was cranking slow but the car would still start.  On my first drive last year it would not start so I replaced the battery.  It started one time then left me stranded after I made a stop at my parents house.  It would not turn over.  I ordered a new starter from the classic center and replaced it.  It starts better than it ever did.  Since it went bad gradually until it failed I just thought my car was hard to start.

[114015]

Franco...

Responds very similar to trying to start when it is not in "Park" or "Neutral".  I know a proper diagnosis discussion is somewhere, but I am reaching out for help finding it.  I am trying to determine if I go directly to replacing the starter motor or if there is are considerations in between.

Have you checked whether all wires going to the starter motor are properly fixed and tight? The starter cable?
Have you checked when you directly connect your battery plus pole with the starter to where the 2.5 violett cable goes? Then your starter motor should jump in. If not the starter needs repair.

Most likely: Your neutral switch on the firewall.
That one becomes faulty as well at age.

Check those devices first.

Malfunctioning starter motors can mostly easily be overhauled.

Good luck,

Achim

[Cees Klumper]

It can also be the ignition switch.

[Cees Klumper]

I also recommend you look into the improved starter motor: smaller, lighter but with more power. Available at a more moderate cost through regular rather than classic car / Mercedes suppliers. There are a number of threads on this, including with contributions from me, including the Bosch part number.

[Pawel66]

It is probably a stupid advise, but this activity saved me several times years ago when I was driving my Fiat 126p and also a couple of years ago with my W463 300GE. I took a medium hammer and hit the starter several times (with some sensitivity, of course,  not to crack anything). This was the issue with brushes that got a bit stuck.

On another event I had to cranck the engine - just a little bit - with gear in, just pushed the car a bit so the crankshaft turns by a degree - sometimes it helps.

When you turn the key - do you hear the starter switch "clunk"? Or it is completely dead? This is the first question.

Other than that - do you get voltage on starter connectors when you should have voltage there? I think this is the second question.

[su8pack1]

I had a similar problem a few years ago. Changed out the starter, replaced the ignition switch, etc. It turned out to be corrosion at a connection attached at the oil pan where the wires connect from the ignition switch to the starter. For a few months I was using a started button under the dash with a direct wire from the temporary starter button switch to battery. When I had more time I started to clean every wire connection I could find until this one solved the starting problem.

[250SLFranco]

Brad....
    I was out..wanted to thank you for your response...Think I may just head straight to replacing the starter motor like you did.
250SLFranco

[250SLFranco]

Hello Cees....
   Wanted to thank you for your input.  I think I will end up with a new starter motor as you suggested.  I have replaced much else over the past 20 years, might as well go for a new starter.  Any idea on average cost for labor and parts?
Thanks again...you have been helpful before.
250SL Franco

[Cees Klumper]

I think you will find all the info here:

https://www.sl113.org/forums/index.php?topic=21743.0

I paid €200 to a French webshop on exchange basis. Putting it in is about an hour's work for someone who knows what they are doing. Good luck!