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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Mercedes Benz Qualified Diagnostic Technician
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2001 a140 petrol usually starts fine but sometimes when ignition

Resolved Question:

2001 a140 petrol usually starts fine but sometimes when ignition key turned dash lights up but starter does not operate.If car left for a couple of hours will start fine even though nothing tampered.Will bump start fine straight away.If car put in gear and rocked still will not start by key.Any suggestions ? Thank you
Submitted: 3 years ago.
Category: Mercedes
Expert:  MB Paul replied 3 years ago.

MB Paul :

Hi,

This is commonly down to an intermittent fault with the starter motor itself. We replace many starter motors for this problem. Less commonly there can be a voltage supply problems, usually caused by a faulty engine control unit.

The problem can be testing it - to prove what is going on it needs to be tested in a failed state to see if voltage is getting to the starter motor or not. If it is tested when everything is working ok then it will not prove anything so it is quite often to have the car in to keep testing to try to get a reading when the fault occurs.

Also to get to the starter itself is a little tricky - the engine & subframe needs to be dropped down to access or replace the starter motor.

There is a connector inside the battery box which is convenient for testing, I would recommend that you (or someone for you) tests here with a volt meter to see if voltage is present. Test with the connector still plugged together by probing in the rear - you are looking for a multi plug with a purple & white wire (see the picture below). This is the voltage supply to the starter. If battery voltage is present here when trying to start the car with the starter not turning then it is likely to be a starter fault (in theory it could still be a wiring fault to the starter but this is extremely unlikely!)

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MB Paul :

Best regards, Paul

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