Fiesta ST MK8 cranks but immediately dies.

[BrunoST]

Hello everyone!
I currently have a 2020 Mk8 Fiesta ST 1.5. This morning I was trying to start the car to go to work but, after pressing down the clutch and pressing the start button the engine would crank (like half a sec) and would immediately die. This happened like 4 times and then it finally started.
No lights on the dash. After getting to work I turned off the car and decided to try to start it again and it did start flawlessly.
During the day I started the car around 4 times to test and it did start with no issues.
Checking the test menu, the battery shows all the correct voltages of the battery, when the engine is off shows around 12V and on shows around 14.5V.
The car has a 7 year warranty extension and Ford wants to charge me around 100€ just to try to diagnose the problem and would only give the money back if they found the issue. I'm afraid to take the car there and spend the 100€ for them to tell me that the car has no problem because it didn't fail in their hands.
Any clues of what's happening?
Best regards,
Bruno

 

[Intuit]

Check for stored codes.

https://www.fiestastforum.com/threads/battery-monitoring-system.25904/post-478335

Have to look at cranking voltages.

Hold the accelerator pedal to the floor before beginning and during the crank.

If the front outlet in the 2020 is always active like it is for my 2016, you can read the voltage during crank from there. Once it's cranking it should hold at least 10.1 easily. But it's that split-second during initial crank that you'll want to pay attention to. Dropping a little below that won't create an issue but it might be worth testing to see whether something as simple as eliminating that voltage dip, has an impact. My 2016 appears to purely off the battery for the first seconds after initial start, before the BMS will ramp up the charge level. (normal behavior for that generation of ST)