Engine stopped at traffic light

[Dylan123]

I need your expertise.

I have 2011 Z4 30i with 202,000 miles on it.
The car is well kept and serviced regularly. The starter, alternator and battery are brand new recently replaced in the dealership.

To my surprise the engine just stopped at a traffic light today. Also, last week I couldn't start the engine for several seconds. It all happened right after filling up the fuel tank, not sure if there's any connection here.

Do you think this is electrical issue (spark plug distributor) or fuel issue (fuel pump)?

I appreciate your help.

[B21]

Hello..there is no distributor on E89s..each plug has its own coil pack…

Really need more to go on..as usual a decent BMW code reader is your essential friend..

[Dylan123]

The code reader that I have didn't give me anything.

It usually shows the code when a warning light is on.

[B21]

Well looks much more like low pressure fuel pump..or something like a crank sensor..

I assume it runs now..what does the LPFP pressure rail say when it’s running..?

[Tangent]

Based on my experience with BMWs over the last couple of decades, if it doesn't repeat, don't worry about it. My Z4 once cranked for 10+ seconds without starting and then started up completely normally the next time. It hasn't repeated in the ~5 years and ~20k miles since then. The 2001 330i I used to have did that on two separate occasions and also immediately fired up on the next attempt and once also just died on me at a traffic light. It also twice had the tach gauge get super sluggish for about 10 seconds while driving and then go back to normal. All those instances were years apart. My best guess is sometimes the DME just goes glitchy for a second or two which is enough to kill an idling engine or prevent a start.

[Dylan123]

Originally Posted by B21

Well looks much more like low pressure fuel pump..or something like a crank sensor..

I assume it runs now..what does the LPFP pressure rail say when it’s running..?

Yes, it runs now, but the problem repeated again (3rd time in 3 weeks) and now I know for sure that this happens after empty tank is filled up.

The engine took several tries to start and definitely the issue comes from the fuel system.

I'm visiting the dealership next week and I'll see what they are going to say about the issue.

How do you check the LPFP pressure?

[B21]

Originally Posted by Dylan123

Yes, it runs now, but the problem repeated again (3rd time in 3 weeks) and now I know for sure that this happens after empty tank is filled up.

The engine took several tries to start and definitely the issue comes from the fuel system.

I'm visiting the dealership next week and I'll see what they are going to say about the issue.

How do you check the LPFP pressure?

The E89 doesn’t have a low pressure fuel pump sensor..so it’s a diagnosis by exclusion..looking at other issues / data to determine the issue…the HPFP readings under load would show deterioration…LPFP failure is relatively rare …the other option is a badly leaking injector ..which is really bad as left unchecked will cause engine damage pretty quickly..

A decent garage is your friend in this case..

[Dylan123]

Just want to make an update here:

I stopped turning off the engine when I'm filling up the gas tank because of difficulties starting the engine after. So, my new work-around routine is the following, don't turn off the engine, the gas tank has to be half-full, otherwise the engine starts choking. I think the incoming stream causes some kind of contamination that chokes the engine.

Have you experience such a thing?

[B21]

Originally Posted by Dylan123

Just want to make an update here:

I stopped turning off the engine when I'm filling up the gas tank because of difficulties starting the engine after. So, my new work-around routine is the following, don't turn off the engine, the gas tank has to be half-full, otherwise the engine starts choking. I think the incoming stream causes some kind of contamination that chokes the engine.

Have you experience such a thing?

Time to put a code reader on it..and/or a decent Indy…you’re grasping at straws..