Intermittent starter fault

[Willthechippie]

My 300TD W124 estate won't start if left for approx 12 hours or more. When trying to start all ignition lights come on, glowplug light goes out but when key is turned to starting position there is nothing (instrument lights dim slightly but there seems to be no power to the starter motor). If held in this position it will usually start (starter motor engages and fires up immediately) after 5 to 20 seconds.
Once started, it behaves fantastically well until it is left unstarted for another long period. This has got progressively worse over the last few months. Of course every time i've taken it to a mechanic it's started no problem! I've cleaned and checked battery terminals to no avail, and am wondering if it could be a loose earth in the starter solenoid or an ignition switch problem. Can anyone help?

 

[dava]

I supose your mechanic did do a drop test on the battery?????

 

[television]

A positive test would be to put a voltmeter onto the small terminal of the starter to see if 12 volts is there when you turn the key to start. the large terminal should have 12v on it all the time.

do this first, and welcome to the forum

 

[bigasotonuk]

Hi, My hunch would be that it is the brushes or the commutater in the starter itself are at fault.
As you say the lights dim when you hold it in the crank position so current is being drawn from something.
I had a similar fault on one of mine i replaced mine though.
But you could try given a good clean inside the motor looking in particular at the comm and brushes

 

[jberks]

On our 202, it wouldn't start. Lights looked fine, dimmed slightly on the turn of the key but it wouldn't even attempt to turn over, not even a click, nothing. We even tried jump leads..... Still nothing.
Put a new battery on and she fired up, first flick of the key.

Mercs aren't like other cars .....!

 

[dava]

Some great suggestions here, but please keep it simple, test the battery first, all the rest are done after the battery is proven to be OK.

 

[Willthechippie]

Many thanks

All these are very useful, many thanks.
I tried jumping with jump leads this morning to see if this would identify a battery problem - no luck, although they were not great jump leads. i'll try again at weekend (a kind neighbour has lent me his car for the rest of week).
If no luck here i'll do a drop test on battery first and then start delving deeper.
I am aware that W124's do suffer from ignition switch problems, and am glad that it seems this is not the case. fingers crossed.
This forum's proving very helpful - i shall start compiling a whole list of queries!
Thanks
P.S how do I empty the envelope symbol on the forum page to show that i've re-visited?