Will not start

Tiny
SDBF75232
  • MEMBER
  • 2011 BMW 328
  • 3.1L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 110,000 MILES
Changed alternator and starter. After running the car for about 35-40 minutes then turn off, run an errand, and come back to the car. The car will not start until it has cooled off for about 2-3 hours.
Friday, June 18th, 2021 AT 10:32 AM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

Do you mean the starter won't engage or it does and the vehicle won't start?

If it does engage and not start, it sounds like a faulty crankshaft position sensor. When they start going bad, they are affected by heat. Once they have time to cool off, they work again.

Take a look through this link. It explains the most common symptoms of a faulty crankshaft position sensor. See if it seems to mirror what you experience.

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

What happens when they fail is spark is lost to the spark plugs. If you want to check for spark when it won't start, here is a link that shows how to check for spark:

https://www.2carpros.com/articles/how-to-test-an-ignition-system

If you determine the sensor is bad, here is a link that shows in general how one is replaced:

https://www.2carpros.com/articles/crankshaft-angle-sensor-replacement

If you look at the attachments below, they are the directions specific to your vehicle for replacement.

Let me know if this helps or if you have other questions.

Take care,

Joe

See pics below.
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Friday, June 18th, 2021 AT 9:15 PM

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