How JustAnswer Works:

  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.

Ask MB Paul Your Own Question

MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Mercedes Benz Qualified Diagnostic Technician
15777119
Type Your Mercedes Question Here...
MB Paul is online now

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!)

Full Size Image

MB Paul :

Best regards, Paul

MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience: Mercedes Benz Qualified Diagnostic Technician
MB Paul and other Mercedes Specialists are ready to help you

What Customers are Saying:

 
 
 
  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil
< Previous | Next >
  • 9 dollars, 2 hours of my time, and I drove away. Your diagnosis was right on the mark. Thank you so much. Phil
  • Lurch. Thank you very much. I had real doubts about this website but your promptness of response, quick followup and to the point answer with picture was incredible. Charles
  • As a single woman, I really appreciate an excellent and affordable opinion.
    Thank you Geordie, I will not hesitate to contact justanswer in the future!
    Sue
  • Another great insight to what may be the problem. I will have my mechanic take a look at it tomorrow. Thanks again, Frank...you do indeed know your stuff. Jim
  • I would (and have) recommend your site to others I was quite satisfied with the quality of the information received, the professional with whom I interacted, and the quick response time. Thanks, and be sure that I'll be back whenever I need a question answered in a hurry. Stephanie P
  • Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help. Mary C.
  • This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!! Alex
 
 
 

Meet The Experts:

 
 
 
  • Matt

    Matt

    Mechanical Engineer

    Satisfied Customers:

    495
    BEng hons Mech engineering, in auto industry 22 years
< Previous | Next >
  • http://ww2.justanswer.com/uploads/35/350matt/2012-6-7_182356_matsavatr.64x64.jpg Matt's Avatar

    Matt

    Mechanical Engineer

    Satisfied Customers:

    495
    BEng hons Mech engineering, in auto industry 22 years
  • http://ww2.justanswer.com/uploads/EU/eurotec/2012-6-11_13153_mpjaphoto.64x64.JPG Marty's Avatar

    Marty

    ASE Certified Technician

    Satisfied Customers:

    21389
    Bosch Certified Master Technician with over 35 years experience in the automotive industry.
  • http://ww2.justanswer.com/uploads/MI/mikeamechanic/2013-4-2_175558_photo.64x64.JPG mike_a_mechanic's Avatar

    mike_a_mechanic

    Mercedes Mechanic

    Satisfied Customers:

    116
    17 years experience as a auto mechanic, foreign and domestic.5 years running my own repair business.
  • http://ww2.justanswer.com/uploads/MB/MBpaul/2013-8-21_204936_paul.64x64.jpg MB Paul's Avatar

    MB Paul

    Mercedes Technician

    Satisfied Customers:

    212
    Mercedes Benz Qualified Diagnostic Technician
  • http://ww2.justanswer.com/uploads/IN/indytech/2013-8-8_102717_SantoDomingo146598x6402.64x64.jpg Greg's Avatar

    Greg

    Technician

    Satisfied Customers:

    1086
    Automotive diagnostic tech
  • http://ww2.justanswer.com/uploads/TE/techmachine/0601821347169_717372168_8940977_39623330_o.64x64.jpg Ross's Avatar

    Ross

    Diagnostic and repair technician

    Satisfied Customers:

    467
    Licensed diagnostic and repair technician