[787B]

Hi all.

It seems like my car is starting to develop low pressure fuel pump issues. It's misfiring on startup sometimes - I think it always happens after it's been driven, then parked for somewhere between 10-20 mins and then started again.

I have error codes:

11B501: High fuel pressure after injection has been released: Pressure too low

11B701: High fuel pressure 2 during or after the injection has been released (2nd set of environmental conditions after time delay): Pressure too low

11B801: High fuel pressure 2 after injection has been released: Pressure too low

My question is, was anyone able to authorise warranty claim when the issue didn't appear during dealer diagnostic? Any tips there, or do I just need to wait until it gets really bad?

Cheers

[Mo T.]

Originally Posted by 787B

Hi all.

It seems like my car is starting to develop low pressure fuel pump issues. It's misfiring on startup sometimes - I think it always happens after it's been driven, then parked for somewhere between 10-20 mins and then started again.

I have error codes:

11B501: High fuel pressure after injection has been released: Pressure too low

11B701: High fuel pressure 2 during or after the injection has been released (2nd set of environmental conditions after time delay): Pressure too low

11B801: High fuel pressure 2 after injection has been released: Pressure too low

My question is, was anyone able to authorise warranty claim when the issue didn't appear during dealer diagnostic? Any tips there, or do I just need to wait until it gets really bad?

Cheers

Hey,

I have the same issue and codes, except the 11B501 code. Instead I have the 119F01 code which means “High fuel pressure 2 when injection is enabled: Pressure too low”. I also have additional codes for the engine stopping without driver influence, because in my case the engine stalled after trying to start, heavily misfiring. But if I try to start again it fires right up, I assume it’s the same for you.

Have you tried to replace your LPFP? I’m finding that it may not be the pump but the fuel pump control module called EKPS that is burning out.

At WOT I’m still making max fuel pressure at the fuel rail and my fuel trims aren’t off, which makes me believe my pumps are fine and the intermittent nature of the problem hints towards an electronic issue, such as the EKPS?

[Maverik259]

Do you typically wait to fill up gas when your light comes on?

[Mo T.]

Tried to further diagnose the issue and hooked up Bimmer Link and watched the fuel pressure on the low pressure side. I found that whenever I turn the car off, the pressure quickly falls from 6.8 bar (operating pressure) to 3.4 bar, could anyone find some documentation to see if this is normal? The pressure drops to nearly 0 bar after a few hours, and when I start it cranks longer than usual or misfires for a bit.

I believe this may be the cause for misfiring/stalling followed by a successful second start, because for cold starts the car primes the LPFP. Even with the pressure being completely bled out of the low pressure system, the cold start would still be smooth due to the programmed priming for cold start. But with warm starts there is no priming; combined with a system that bleeds out, you get rough starts on the first attempt and then later a good second start due to pressure now being built within the system.

I know most fuel systems have a check valve to retain pressure in the lines for quick and smooth start up, does the F90 have one intergrated in the LPFP? Maybe that’s why dealers replace the LPFP when these issues occur?

If the system is not designed to loose that much pressure so quickly I don’t think the EKPS module is at fault. To make a case with warranty, you could point them towards to watch the pressure immediately decrease in the low pressure fuel system at shut off.