Starter motor not engaging from the key

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Mon, 08/11/2021 - 00:33
Constable666
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Hi I have a 1993 G300 I have a problem 1. The starter has stopped being turned over by the key. Ignition lock works perfectly. I've had to wire a 12v lead from the starter solenoid break in box on the bulk head to a push button hidden under the dash to Start. I've asked countless mercedes dealership next to useless. Is there a starter relay?
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Mon, 08/11/2021 - 10:55
#1
Jdring
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Re: Starter motor not engaging from the key

Just thinking out loud here.  You probably worked through this yourself.

Could be the ignition barrel itself.  Your'd need to get to the wiring loom to it, know the wire for the starter and see it if gets power on key turn.  Then there must be a starter relay!   But its integrated into the start motor to take high current directly.  Anyway, if you wired in a push button for this, the relay must be working. So I am back to thinking the ignition barrel :(

Here is a fuse allocation chart, for 463, but no starter relay fuse. http://www.fourbyfourclub.com/Manuals/W463249FuseDesignation.pdf 

There is wiring information in the Members section if you can get to those.

http://www.gwoa.co.uk/sites/default/files/download_pdf/Wiring%20Diagrams...

This is showing all the sensors, relays, fuse locations. elec components.  In 27.1 there is a G300 wiring layout for the automatic (because starter is blocked if not in P/N) and it says d is the wire to starter, and its red.  I've attached a screenshot.

The full wiring is 54.2  (copied/attached if readable).  See the legend and the last one - I blew it up.  S2/1 is the switch.  M1 is the starter.  The 12Volt is on the left hand side.

 

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Tue, 09/11/2021 - 20:19
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gav.helme
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Re: Starter motor not engaging from the key

If automatic then starter inhibitor switch on the left side of the gearbox is favourite 

Also check the wiring to it

Black and White plastic unit exposed to all the crap! 
 

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Sat, 13/11/2021 - 07:29
#3
Constable666
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Re: Starter motor not engaging from the key
Hi Thanks for all your points. Yes it is an automatic so will check the box on the side of the G box. When I took ignition to bits not the barrel had a large rubber plug on it. This in turn had about 7 wires coming of it. Hence why I asked if it goes to some thing prior to going to the starter motor. I will thumb through all the above points and repost Thanks Nick
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Sun, 14/11/2021 - 06:58
#4
gav.helme
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Re: Starter motor not engaging from the key

Did you get sorted?

The more I thought about this it could be worth trying an ignition switch as they do go faulty

I have some used ones I could post to you to try 

Quite easy just to swap the wiring plug over and start with a screwdriver before fitting properly 

Although if it works I'd be tempted to opt for a new one at around £75

 

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Sun, 14/11/2021 - 07:59
#5
gav.helme
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Re: Starter motor not engaging from the key

Just for info...

The Starter Inhibitor switch on the gearbox is part number A0005454906 and also is the reverse light switch on the auto

Are your reverse lights working?

Have you cycled the gear lever thru P R N D a few times and tried starting in different positions in case something is out of adjustment at the lever? Perhaps hold the lever against some slight pressure in P or N and try in case something is worn?

Ignition switch is A1164620093 and common with 460 and many MB models of the era

No specific Starter Relay fitted 

might be worth checking the fuse in the overload relay just in case but a long shot for this fault

Only other thing I can think of is have you a broken earth somewhere? Think there is an earth strap from the bulkhead to the rear of the cylinder head.. I've seen these left off after head gasket change causing issues, also is the main battery earth in good order etc 

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