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Discussion Starter #1
Hi all

My M5 died a week or so ago and now it won't start again. Driving to the end of my road with a bit of enthusiasm and just before I stopped at the junction the car died with iDrive giving battery fault, right before it died it felt like it chucked itself into park or changed down incorrectly but I can't be sure. Trying to start it at this point result in a loud click from the engine bay but no go. I knew the battery needed replacing as I got a warning if I didn't use the car for a week so thought it was just that. Went out and got a brand new battery, charged it up and tried starting the car, result was a little bit different this time, loud whirring noise but then went back to clicking. This weekend I charged it back up again and connected jump leads to my 535D, when trying to start the engine actually turned and it sounded like it was about to start but again then back to whirring then the click. Charged it up again today and connected jump leads to my 535D and X5 35D, thinking this would give enough amps to get the car turning over properly but still no joy. I've done a video showing today's attempt but I'm really at a loss of what's actually wrong and how to fix. I have read the codes using ISTAGUI, there were loads referencing low voltages and signal issues but I've cleared them and they haven't come back.

If anyone has any clues on this I'd be hugely appreciative, check the video out here BMW F10 M5 Won't Start
 

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I'd try recharging the new battery again and hook the jump cables from the tractor on in parallel only do it from the back of the car direct onto the battery terminals.
That said, the second cranking attempt sounded a bit off, like the starter motor was turning but against a very heavy resistance.
 

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Discussion Starter #5
Realised I had bought the wrong battery, 95Ah instead of 105Ah. I've been out and bought the correct one and fully charged that along with the 95Ah and tried again but still no joy. I tried again at the weekend and the engine spun slow but for a split second sped up to the point where I thought it was going to start but then went back to the click. I noticed my Xenons were trying to kick in each time so I've removed the main fuses for the lights to lessen the draw on the battery(s). I've tried again tonight but no turning today, just a click and then a low humming sound of something spinning until I take my foot off the brake or start button. I've found a 2nd hand starter on eBay for less than £100, I'm wondering whether to give this a whirl, hopefully they aren't too much of a sod to fit if I go down that route.

@snowblind Your comment about heavy resistance has got me wondering.. Is it worth taking the spark plugs out and trying to turn it over? I suppose if I did that I could borascope down in the cylinders although I really wouldn't have a clue what I'm looking for to be honest.
 

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Discussion Starter #7
I've got ISTA gui setup on one of my laptops, I've read the codes and there's nothing showing other than a pedestrian sensor error but that's been there for months. When you say read the status, do you mean read the live figures on certain components? I monitored the status of battery voltage and amps during one attempt of starting, the volts went from 12v down to 9.5v and the amps shot up from 25 to 700+. Should I be reading the status of anything else?

I'm going to attempt to turn the engine by hand over the weekend, see what joy that brings me
 

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Having read the posts it looks very much like the starter motor is at fault. If it is failing to spin the engine over correctly even with a fully charged battery I would be whipping it out and see what shape it’s in.
cheers
jim
 

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Hi, I have noticed that some of my device voltages have dropped to under 10 volts which is not good and as a result have ordered a new battery. You can perform a vehicle inspection to check for warnings and errors which might shine some light on the issue. Another idea is to pull the battery and let everything reset and see if that helps.
 
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