Cranks, no start

[Star Nick]

Good day Bimmers
I trust you are good guys
Please help me, I'm desperate to figure out what's going on, and neither the mechanic nor the dealership have any good ideas!
I have had my wonderful 2011 BMW e90 320i for 4 years, and until now it's been great fun to drive with hardly any problems.
It starts fine the first trip of the day. However, after driving a while, usually very long distances but occasionally while running errands around town, I will get back in the car and attempt to begin the next leg of my trip, but now the car won't start. It does crank but it wont start. The dash lights come on, but then nothing. Eventually, sometimes 30/40 minutes later sometimes hours later, the car will start just fine like nothing ever happened. :dunno:
I have this problem everytime I drive the car. The car was serviced last year August, but I started experiencing this problem in December, since then I have replaced, there is no warning lights
Crank Sensor
Starter brushes/solenoid
Fuel pump
Spark plugs
Tappit cover gasket
Battery
The car still has the same symptoms even though I have replaced all of those
My guess is that the brand new battery somehow compensated for whatever is causing the problem.
It is so inconsistent that the dealership could not duplicate the problem, even after I drove it hard for almost 2 hours. But when I am alone on the road and stop for gas or a restroom, I am almost guaranteed to be stranded.
I am out of ideas at what to look at, please advice
Thanks for any ideas!

 

[TurboLlew]

I assume if you had it at the dealer they would have already read any stored codes? I know the newer cars will store codes related to starting issues even though they don't have lights on the dash. I am not sure if the E90 has a starter relay or if it is part of a module. The relay is fairly easy to swap out if it is sticky (and you'd hear it in the fuse box).

If it is a faulty module (not generating a code or not sending a signal) that would point to your CAS unit. This is fairly common in terms of modules that 'go bad' due to surges/boosting/low voltages etc. With the car cranking though, the CAS is obviously sending a signal to the starter.

That leaves ignition or injectors which could point to a wiring issue or your DME. It is also not unheard of for the DME to develop issues over time.

On the hardware side, you seem to have ruled out all the obvious culprits. One last resort you may want to explore (which I had on another car a long long time ago) is to look for loose earth cables. This may be ANY location but likely close to starter, alternator and DME locations. On my Subaru it was sending a crank signal but required a stronger ground than the loose connection was allowing to get coil drivers to function reliably when hot. The ECU made it easy to figure out that there was an ignition issue but not obvious at all that a stupid little ground strap to the intake manifold was the actual cause of it not starting.

EDIT:

to give you an idea of how dumb this problem was: that bolt holding the black wire on the red intake manifold was loose...

 

[General.Massacre]

depending on your vehicle specs, the car might have an IBS sensor on the Battery Negative terminal, check that that is plugged in, and/or the IBS is grounded correctly to the chassis.
Could be that the IBS is faulty, or it was not carefully undone when the battery was last replaced.

 

[A.C.SCHNITZER]

I was taught to replace cam and crank sensor at the same time as they work hand in hand, if 1 is faulty sooner or later the other 1 will die too. I would suggest you diagnose the car with INPA or Launch scanner and get DTC. Good L:uck

 

[kefrens]

If you rev it, does it start?

 

[firaz]

Leaking injector. That’s my hunch.
Replace all, alternatively if you can find the faulty one.


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