S54 Intermittently long slow cold start

[Ascanio]

1) It doesn’t seem to depend on ambient temperature. It happens 75% of mornings regardless of whether it was a cold night or not.
2) It doesn’t seem to depend on fuel quality, I am switching between different brands of 93 Octane.
3) It doesn’t seem to depend on battery, I have tried the charging it overnight with a BMW branded charger. Same old.
4) It shouldn’t be a fuel pressure issue because I let the key stay in the ACC position a few seconds always before cranking (unless the fuel pump for some reason doesn’t start until the engine is cranking, which would be very weird… BUT, I admit I can’t hear any sound of pump with engine OFF and key in ACC position).
5) It feels initially like a near dead battery, the engine will crank slowly, and the lights in the dash (like Check Engine Soon) will flash rapidly while cranking. This morning I had two failed cranks like that, lasting 2 to 4 seconds each. Then the third crank was nice and fast, no flashing telltales and engine fired up after less than a second.

- Could it be fuel pump going bad? I have no issues once the engine is running.
- Could it be fuel filter(s)? Again no issue while running.
- Could it be the starter motor going bad?
- Could it be spark plugs or other electrical?

[Ascanio]

UPDATE: I think I found the culprit, seems to be the fuel pressure.
If I wait, much longer, after having turned the key to ACC, to start cranking, all is good in the world.

So I turn the key, wait for the Nav screen to flip up, and for the dynamic rev limit indicator to set. Then I crank. No slow or long crank anymore

[Finnegan]

It's great you found what seems to be a fix. Still seems odd to me though. Even after a couple of weeks or more of sitting this isn't my experience with the S54.

Are you able to read any codes?

[SunUpTopDown3]

This is standard procedure for me now. I except no nav screen . I always turn the key furthest it can go without cranking the car. let it stay like that for a bit while it beeps away I open the garage, put gloves on etc.. then I crank the car. Fires up quickly and easily. Just a habit now.

[Ascanio]

I am getting closer to the culprit!
Have discovered that if I switch OFF the radio before a cold start, the engine cranks perfectly.
There must be something wrong with the radio unit or the amp.

[Ascanio]

Nope wasn’t the radio.
It’s about how I kill the engine when parking: if I keep the engine idling for 30 seconds after having moved into the spot, the car will start OK.
If I kill it just after having clutched the last few inches into position, I get long cold start