I am driving BMW 530d 2006 model car. After driving some kilometers and stopping the car, when I try to start again, the car doesn't start. It will start after 10 to 12 hours of resting. Please help me.

  • To whoever voted to close: please check if the post is salvageable by formatting, grammar and spelling fixes, by checking the tags and by checking the title is okay. This post was salvageable. – juhist Sep 12 '17 at 12:17
  • Fuel starvation could also cause this - check that the fuel system is vented as it should be. – Solar Mike Sep 12 '17 at 12:44
  • This is a bit short on details. Does the engine crank at all when you hit the start button? Do you have any warning lights? Have there been any other problems or repairs recently? – GdD Sep 12 '17 at 13:37
  • As others mention this needs lots more detail... – Solar Mike Sep 12 '17 at 14:12
  • Does it crank strongly and not start (whirrr, whirrr, whirrr), or does it crank slowly (w h i r r r r r rump) and not start, or does it not crank at all? The first instance is likely fuel pressure/volume, perhaps a bad fuel filter. The second is likely bad battery/starter cables, which increase resistance with heat, but seem fine when cooled off. The third could be any number of electrical or fuel problems, also probably with heat as a root cause. Other comments are spot-on, the problem might be salvagable, but the post needs much more detail to even speculate. – SteveRacer Sep 13 '17 at 0:27

This may be related to the coolant temperature sensor. When the car is warm, if the coolant temperature sensor is broken, it might indicate the engine is cold, and then the ECU tries to start a warm engine like it would start a cold engine.

After 10 to 12 hours of rest, the engine has become cold again, and now the procedure to start it like a cold engine works well.

Of course, your battery and/or alternator might be dying, and the 10 to 12 hours of rest may be enough for the battery to be able to provide some juice for starting the car.

Does the starter motor crank well in the no-start condition? If it is cranking well, the problem is probably the coolant temperature sensor, and if not cranking well, the problem may be in the alternator and/or battery.

Do note that there may be multiple coolant temperature sensors. Some control the radiator fan, some display the temperature on the dashboard, and some feed the ECU with coolant temperature information. The one that feeds the ECU with coolant temperature information is the relevant one here.

  • good answer... the symptoms the OP describes are very similar to what I experienced when my coolant temp sensor had failed. – motosubatsu Nov 13 '17 at 10:22

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