Z4 e89 won’t start
- Thread starter AdamZ4
- Start date
matsmith749
Active member
I think you're on the righ ttrack - definitely sounds like Irritable Bowel Syndrome.
A car battery shouldn't really be showing 14v unless the engine is running. It should be around 12.6
Scottish Borders
Rockhopper said:
E89 battery voltage can be all over the place for many reasons as it’s not controlled by the alternator / voltage regulator but the DME..my digital dash allows me to show bus voltage…and it’s all over the place ..on the overrun it will hit 14.5+ and on acceleration it drops to 11.8…plus many other changes..
FWIW with a conventional alternator / regulator you would expect the off load voltage to be around 14.5v to 24.8v
Yeh but he’s saying it won’t start yet the battery is showing 14 volts
matsmith749
Active member
Voltage isn't what makes the battery capable of supporting engine start - its the ability to provide enough CCA (cold crank amps).
This is how batteries deplete over time - it may look like you have some volts, but the second you turn the key (or push the button) the volts will drop to <10 & there isn't the capacity needed to power all the electronics & the starter motor at the same time.
Hence a failing battery will look fine, even if it has just come off the charger & says it is full - but will not start the car. Worst case is it starts the car once, then you drive somewhere.... and then it won't start! (ask me how I know)
Age is a good check failing proper test equipment, if >5 years & you are seeing electrical gremlins, get it replaced.
This is how batteries deplete over time - it may look like you have some volts, but the second you turn the key (or push the button) the volts will drop to <10 & there isn't the capacity needed to power all the electronics & the starter motor at the same time.
Hence a failing battery will look fine, even if it has just come off the charger & says it is full - but will not start the car. Worst case is it starts the car once, then you drive somewhere.... and then it won't start! (ask me how I know)
Age is a good check failing proper test equipment, if >5 years & you are seeing electrical gremlins, get it replaced.
I bought my Z4 in good faith from a reputable dealer. However, after a couple of months dash lit up like a Christmas Tree. Power steering, would not start properly, ABS, fuel pump, dials, handbrake etc. At one stage had 33 different fault on my ISTA, Car drove absolutely fine. I took it to both BMW (who were not very helpful unless i parted with vast amounts of money.) Took it to Independent BM specialist who couldn't figure it out. I spoke with an ECU specialist who has worked for weeks on it. The outcome was a shock.
The DME (ECU) module was cloned incorrectly by the previous owners of the vehicle and an attempt to repair the hardware was poor to say the least. However they were successful in repairing it. They managed to retrieve the relevant data after some time.
Upon preparing the donor ECU, we were met met the same problem. The donor ECU, although not damaged, had been cloned before. When MSV80 ECUs are cloned, there is an extra step required to ensure the ECU allows modification in future. If done incorrectly, this permanently locks the ECU into a read only module.
I am happy to confirm that today they will be returned to you with a positive outcome.
It just shows you what can happen when you buy a car in good faith. This is obviously a common issue and to be honest BMW just ignore it.
The DME (ECU) module was cloned incorrectly by the previous owners of the vehicle and an attempt to repair the hardware was poor to say the least. However they were successful in repairing it. They managed to retrieve the relevant data after some time.
Upon preparing the donor ECU, we were met met the same problem. The donor ECU, although not damaged, had been cloned before. When MSV80 ECUs are cloned, there is an extra step required to ensure the ECU allows modification in future. If done incorrectly, this permanently locks the ECU into a read only module.
I am happy to confirm that today they will be returned to you with a positive outcome.
It just shows you what can happen when you buy a car in good faith. This is obviously a common issue and to be honest BMW just ignore it.
