Car wont start

Tiny
EDWINKE
  • MEMBER
  • 2008 BMW 520
  • 2.0L
  • AUTOMATIC
  • 124,274 MILES
I have changed the battery because it would not start after a some time. Then after two weeks the car will not start again. I changed the starter, but the car will not start. Any ideas?
Do you
have the same problem?
Yes
No
Wednesday, July 27th, 2016 AT 8:33 AM

8 Replies

Tiny
CARADIODOC
  • EXPERT
"Will not start" can mean a number of symptoms. Do you mean the starter would not crank the engine, it cranked too slowly to start, or it cranked normally but the engine would not run?

If the starter was cranking slower and slower over a period of days or weeks, that suggests the battery was not being recharged while you were driving. That's a charging system problem, not a starter problem. Charge the battery at a slow rate for an hour with a portable charger, then have the charging system tested. You can start the test yourself with an inexpensive digital voltmeter. Measure the battery voltage with the engine running. It must be between 13.75 and 14.75 volts. If it is low, suspect the generator or voltage regulator. If it is okay, that only means it is okay to perform the rest of the tests, but that requires a professional load tester. Your mechanic will measure the full-load output current and "ripple" voltage. There are six diodes in every AC generator. If one of them fails, you will lose exactly two thirds of the generator''s capacity. 30 amps from a common 90 amp generator is not enough to meet the demands of the electrical system under all conditions. The battery will have to make up the difference until it slowly runs down over days or weeks.

All AC generators produce three-phase output. One phase will be missing when a diode has failed. That causes output voltage to drop quite a bit during that missing current pulse. That is where ripple voltage is a clue. That is the variation between the highest and the lowest voltages the generator is developing. With a failed diode, ripple voltage will be very high. Some testers actually measure the amount of ripple voltage, but knowing that is of little use. Most testers just show it on a relative scale. "Low is good; high is not good".
Was this
answer
helpful?
Yes
No
Wednesday, July 27th, 2016 AT 7:07 PM
Tiny
EDWINKE
  • MEMBER
No its not doing nothing, the engine light on the board lights up and the message "ignition switched on" show up on GPS, the engine does not make any noise only the front and back lights go on.I tried with another key after one and half to two hours and the car start, after that I stopped the car and try the previous key and that works too. I am so confused, I do not know what is the problem. Now I need to go with two keys everywhere.
Was this
answer
helpful?
Yes
No
Thursday, July 28th, 2016 AT 12:40 PM
Tiny
SATURNTECH9
  • EXPERT
Just to add to this one on that car when you change the battery you have to have the battery module computer reset to tell it you got a new battery. Otherwise the battery can be damaged. Also your going to have to take it somewhere that knows about BMW's and have all the computers scanned. To see what is going on with your key issues. A car like that is a really hard to work on for a diy-er it takes special tools professional scan tool etc. Just to get a starting point on what to look at where to go.
Was this
answer
helpful?
Yes
No
Thursday, July 28th, 2016 AT 1:13 PM
Tiny
CARADIODOC
  • EXPERT
Thanks Saturntech9.
Was this
answer
helpful?
Yes
No
Friday, July 29th, 2016 AT 12:14 AM
Tiny
EDWINKE
  • MEMBER
When I go with the car to the bmw service they tell me everything is okey nothing bad with the computer or any other problem and after the batery was changed they reset the computer and set the settings for that batery. The only thing they didnt check was the keys, and I rly hope its just the keys and anything else its okey.
Was this
answer
helpful?
Yes
No
Friday, July 29th, 2016 AT 12:21 AM
Tiny
SATURNTECH9
  • EXPERT
Is it always the same key that gives you trouble or both of the keys?When battery's go bad in cars like that sometimes they have issues with recognizing keys etc It might just be that the keys need to be just reprogrammed to the immobilizer.
Was this
answer
helpful?
Yes
No
Friday, July 29th, 2016 AT 7:12 AM
Tiny
EDWINKE
  • MEMBER
Yes I use the same key because the other 2 dont activate something on the gps like not showing consum or km to destination the right side of the gps is not working with them.
Was this
answer
helpful?
Yes
No
Saturday, July 30th, 2016 AT 5:21 AM
Tiny
SATURNTECH9
  • EXPERT
If one key always works and the other two don't then I would have to say it really sounds like a intermittent bad key issue.
Was this
answer
helpful?
Yes
No
Saturday, July 30th, 2016 AT 12:08 PM

Please login or register to post a reply.

Recommended Guides