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Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 20394
Experience:  BEng hons Mech engineering, in auto industry 22 years
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Currently non starter and cant figure out why, well its and

Customer Question

currently non starter and cant figure out why
JA: When you turn the key, do you get a single loud click, or a series of rapid ones?
Customer: well its and sorry an e90 with a button start and when you press once for ignition the fuel pump runs continuously
JA: What is the model/year of your BMW?
Customer: 2006 e90 320d m sport
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: i have investigated a very noisy dme relay in the ecu box which after unplugging and plugging back in has gone silent and have looked into the pump as it runs and there just seemes to be foamy diesel coming back through what i suppose is the return feed.
JA: Anything else you want the mechanic to know before I connect you?
Customer: well the car worked fine i was driving home late on thursday night and it wasnt until i went to use it again early friday afternoon that it wouldnt start and at first it would turn over until i switched it of wheras anw it barely turns once and the battery is at 12V. the only possible circumstance that could have caused any problem is that on thursday night i was driving in very very heavy rain so possible water damage somewhere but i dont know where.
Submitted: 1 month ago.
Category: UK Car
Expert:  Matt replied 1 month ago.


if the car's no longer cranking / turning over 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

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