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Matt, Engineer
Category: Mercedes
Satisfied Customers: 21246
Experience:  Mechanical Engineer with 23 years experience in the auto industry, 8 yrs in formula 1 engine testing
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Started twice and shut down on idle wont engage starter now,

Customer Question

started twice and shut down on idle wont engage starter now
JA: Have you checked the battery, particularly the terminal connections? Are they corroded?
Customer: all checked even put jump start on all dash lights come on and wont go out hazard light aswell
JA: What is the model/year of your Mercedes?
Customer: ml 500 2002
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: nothing could battery be down 1amp maybe
JA: Anything else you want the mechanic to know before I connect you?
Customer: no it just started twice and shut down by its self has fuel wont even crank over 230000 km no problems before this drove sweat as 2 hours before thanks
Submitted: 6 months ago.
Category: Mercedes
Expert:  Matt replied 6 months ago.

If the car's not cranking then first check it can turned over by hand so double checking for any mechanical issues

If OK then check that the main battery cables are on tight and the terminals are clean and bright. Do the same for the engine / gearbox earth strap.
Then follow the main positive lead back to the engine and down to the starter motor, and check the connection at this end as well.

There should also be a small wire to the motor which should have 12V when you're turning the ignition switch to crank. If the 12V isn't there, check back along this wire for damage to the insulation or corroded connections

This 12V feed comes directly from the ignition switch so this may be faulty and need replacing

Check the resistance of the main positive lead that runs down to the motor as anything more than a few ohms and it should be replaced

Don't forget to try a jump start from another car / battery as its possible the battery is poor, if you have a voltmeter a healthy battery should read 12.7+V

also try substituting the battery for another as I've known a very flat battery to drag down the system voltage too far even with jump cables

one other thing to consider is that the immobiliser is faulty and preventing the starter from being enabled - however if the dash / ignition lights are on then this usually means that its off

If this is all OK then its possible the car needs a new starter motor