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Discussion Starter #1
Hi Guys

We have a really frustrating intermittent starting problem on our r53, We've only had the car 5 or 6 weeks and have been having this problem for about 3 weeks now!

So basically pretty much every morning seemingly more so when its colder, it struggles to start sometime it will take a couple of attempts others 15 or 16 attempts, once its been driven to work and then restarted to come home 10 plus hours later it pretty much starts every time, but every now and then an hour or 2 after being driven it struggles again!

It seemed to have a week spark when not starting and not firing and the voltage at the battery would also drop to about 9.5 volts, I'm unsure if this 9.5 volts would be normal as the starter motor would be drawing quite a lot of current, the alternator is giving 14 volts at the battery when running and when running has a big fat spark considerably different to when not starting

So with these figures I thought that weak spark was the problem, so I've replaced the coil pack, plugs and leads as they were still the original 9yrs old

The next morning still the same problem, I then wondered if the battery dropping to 9 volts was the problem so when cold hooked up my big van battery to the mini battery without my van running so only battery voltage was available not 14 volts from my alternator and it started first time stupidly I didn't measure the voltage when the engine was turning to see what it dropped down to

The last few weeks I've been working away so haven't been about to try anything else but the first week my sister dropped it of at the garage we use so they could have a look at it, of course sods law it started every time for them when cold, I told them everything I'd tried and they did the same they checked the battery as well and said it was fine

so last week my sister had the car back again and of course we have the same problem, the garage to it too I know well and they've worked on our cars for the past 15 yrs and I've every confidence in them so am pretty sure they're telling the truth when they say it never had the fault when they had it

I've obviously done quite a bit of research on here to try and diagnose the fault, I understand there is a fairly common fuel pressure problem that requires the engine to be turning for a little while before it starts to build the pressure up again, but don't think it is this as sometimes our engine will literally be turning for 60secs before it will start

I'm still fairly sure its weak spark that's the problem as opposed to fuelling I'm suspicious about the battery but don't want to start chucking parts at it in the hope that something will work

I'm not going to get another chance to plat about with it some more until next weekend, but plan to hook up the van battery again and disconnect the plug to the coil pack so it wont start to see what the voltage drops to when turning but not firing, I'm going to check the engine earth straps and replace of necessary in case these have any continuity issues

Its been plugged into a fault code reader at the garage and showed no faults either!

I understand the engine temperature changes fuelling when cold but wouldn't have thought it would have had an effect on ignition, but I'm tempted to change this as well as a matter of course

So if anyone out there has had similar issues or got any ideas or can tell me I've overlooked something massively obvious then we'd really appreciate it

Thanks in advance
 

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how about the crank sensor
had a similar issue with my lads clio 172, replaced the sensor and it has been fine since
might be worth a shot
 

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Discussion Starter #3
Thanks

I'll give bmw a bell tomorrow to check price and availability and on a cam sensor as well

Still no recorded faults on the odb for any sensor though!

Thanks for the idea
 

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Thanks

I'll give bmw a bell tomorrow to check price and availability and on a cam sensor as well

Still no recorded faults on the odb for any sensor though!

Thanks for the idea
So I had a similar problem and it turned out after my own mechanics inspected an electrical or wiring issue sent me to mini. They scanned it turned out to be crank shaft harmonic dampener and my bpv It wouldn’t code on a regular code read except p1658 which was an error with the electronic throttle body. Now it drives every time and I am finally making full boost
 

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Double check your ground points as well, I have been experiencing starter issues the last few days, found that the ground point on the engine mount was snapped and the strap was barely contacting.
 
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