[Ondras]

Hello helpful people, I have a weird problem on my 2013 528i - N20 engine (4 cylinders 2.0) twin turbo.
- Cold start - perfect, within a second, holds idle
- Operating temp start - once engine is fully warmed up, within few minutes after it's been shut off. - starts perfect, within a second, holds idle
- when then the engine is cooling down - about 10 - 30 mins after it was fully warm and shut off - the dashboard temp gauge shows between 70 - 90 deg. C. - It starts but really low idle and dies a few seconds after. It runs enough to start driving but then loses power, pressing gas does not help and dies in the middle of the road. Trying to start again, it cranks gets sort of running but very low rpm and dies right away. Wait for it to cool down more - 10 - 20 minutes, starts again fine, or with some help - pushing the gas to around 2000rpm, then let go of the gas, it settles on good idle and runs fine. The car runs super smooth, with no issues except this.

There is no engine light coming on when this happens. But sometimes it saves an error code - "high pressure fuel pump - low pressure" or something like that. I got it diagnosed, and that's the only error code that is recorded. I've replaced the high pressure fuel pump, but same problem remains.
It is not always easy to reproduce, had it in a shop for a week, but as it did not happen, they could not troubleshoot - measure stuff as it happens.

What would be the recommended steps to check without wasting money or replacing a whole bunch of things without a clear fault found?
I am sure this happened to others and would love to know what solved it.

Thanks so much in advance.

[Ondras]

The engine runs very smoothly when driving. But what happened a couple of times, when stuck in traffic and idling and inching forward, engine hot, cooling fan coming on and off, after about 20 minutes it died and could not start again till it cooled to about 70 deg C. I cannot describe how frustrating and stressful it is to not know if/when it's going to die.

[chipguy]

Do you have a scan tool that can read the fuel pressure at the rails? If you do, monitor the fuel pressure and hopefully there is come correlation.

[Ondras]

Thanks, chipguy. I don't have a scan tool for pressure in the rail.
I've changed the high-pressure fuel pump, and next, I will change the high-pressure fuel sensor and camshaft position sensors. I've checked the intake for vacuum leaks. Did not find any. Something is giving some wrong data to the ECU at specific temperatures. Otherwise, everything runs perfectly. Logically it must be something in the engine bay giving an incorrect reading - sometimes when it's warm.

[Ondras]

It's been a few months now, I am happy to share that the issue is solved. After replacing the camshaft position sensors the issue did not reappear in any situation. I've driven and tested it extensively.

[Ondras]

The issue is back
I got Carly, and measured the Rail pressure - it sometimes drops to 0.5MPa and dies. and cannot restart. normal idle rail pressure is 7.5MPa, at acceleration 20MPa before start it builds up to 12MPa and then slowly drops down to 7.5. But sometimes when the engine was restarted from half warm, it drops under 0 and these is not enough fuel, the engine coughs and dies. Any ideas why would the fuel pressure at the rail drop sometimes, but run perfectly fine 99% of the time? I can drive the car for 10 hours straight without switching the engine off and it runs perfectly. After I stop the engine and wait for bit, it gets to this weird mode when it does not build up the fuel pressure.

[Ondras]

just to add, I replaced the High-pressure fuel pump and the pressure sensor on the rail a few months ago. OEM. So this cannot be the reason. And if the low-pressure pump in the tank was faulty, it would not run 99% of the time.

[Ondras]

Hello chipguy - curious to hear what you think about this. The ECU shuts down the fuel pressure. But no clue why.

[ChiltiCoatl89]

Originally Posted by Ondras

Hello helpful people, I have a weird problem on my 2013 528i - N20 engine (4 cylinders 2.0) twin turbo.
- Cold start - perfect, within a second, holds idle
- Operating temp start - once engine is fully warmed up, within few minutes after it's been shut off. - starts perfect, within a second, holds idle
- when then the engine is cooling down - about 10 - 30 mins after it was fully warm and shut off - the dashboard temp gauge shows between 70 - 90 deg. C. - It starts but really low idle and dies a few seconds after. It runs enough to start driving but then loses power, pressing gas does not help and dies in the middle of the road. Trying to start again, it cranks gets sort of running but very low rpm and dies right away. Wait for it to cool down more - 10 - 20 minutes, starts again fine, or with some help - pushing the gas to around 2000rpm, then let go of the gas, it settles on good idle and runs fine. The car runs super smooth, with no issues except this.

There is no engine light coming on when this happens. But sometimes it saves an error code - "high pressure fuel pump - low pressure" or something like that. I got it diagnosed, and that's the only error code that is recorded. I've replaced the high pressure fuel pump, but same problem remains.
It is not always easy to reproduce, had it in a shop for a week, but as it did not happen, they could not troubleshoot - measure stuff as it happens.

What would be the recommended steps to check without wasting money or replacing a whole bunch of things without a clear fault found?
I am sure this happened to others and would love to know what solved it.

Thanks so much in advance.

LPFP? especially with the N20, that you have a single turbo, twin scroll turbocharger What gas do you use? and have you used a nice Fuel cleaner?

[ChiltiCoatl89]

I am looking more into what you are experiencing.

[ChiltiCoatl89]

Originally Posted by Ondras

just to add, I replaced the High-pressure fuel pump and the pressure sensor on the rail a few months ago. OEM. So this cannot be the reason. And if the low-pressure pump in the tank was faulty, it would not run 99% of the time.

Be sure the connections on your new installed parts are nice and firm, not too tight, rather, torqued to spec. How many miles or Kilometers does your Car have?

[ChiltiCoatl89]

If you use a nice Fuel system cleaner, also clean your MAF Sensor.

[Ondras]

I got Carly - to monitor the error codes and bunch of sensors. The car has 130k km, and new engine block only 27k km. New HPFP, new fuel pressure/temp sensor on the rail. New battery, new coolant pump, new control unit (EKPS) for the low pressure fuel pump in the tank.
This is what is happening - cold start - runs perfectly, engine warms up, oil and coolant temperature as should be fuel pressure at the rail - as should be 75-200bars. I can run it for 10 hours, with no problems when driving, including stopping and stop/start on or off - all good. I did 20k km with this issue, it's very consistent. When I stop the engine and it's warm - the engine bay really warms up with the heat soak. after about 15-20 minutes - I put on the ignition, and the fuel pressure is around 120 bars, it starts fine, but after about 15-20 seconds - the fuel pressure suddenly drops and the engine dies - within 2 seconds the pressure is at 5 bars. What can cause the pressure to drop suddenly? in all other situations, it never happens. After the pressure drops, it does not build up, until I let the engine bay cool down - another 15-20 minutes - with the hood open it speeds to cooling down. After that it started fine, the fuel pressure was all good, just like nothing happened. And I can drive with no problems till the next stop. it only happened to me once when I got stuck in traffic, on a very hot day, 20 minutes in a jam, inching forward, between D and N - it died on me. And could not start again - till cooled down again a bit. It must be something in the engine bay that gets hot and sends the wrong info to the CPU or the EKPS. but what could it be? The EKPS was changed just today, coded and all the computers updated with the latest SW - at an authorized BMW service.

[Ondras]

Originally Posted by ChiltiCoatl89

LPFP? especially with the N20, that you have a single turbo, twin scroll turbocharger What gas do you use? and have you used a nice Fuel cleaner?

I use 89 gas. How could fuel cause an intermittent issue that only happens in specific engine bay temperature conditions?
Or how could LPFP stop working only in those specific conditions? I really don't want to keep replacing more parts that are perfectly fine while the issue persists.

[Ondras]

What I don't get is - how an authorized BMW service is not able to troubleshoot this.? I shared all these details with them. All they do is: look at the error codes, try to replace one part after another and see what happens.
11A401 - High-pressure fuel injection upon release: too low pressure
11B401 - High-pressure fuel at or after the release of injection (second environmental condition set by time delay) to low pressure
What does "second environmental condition set by time delay" actually mean?

I know there is low fuel pressure at the rail and I know the exact pressure it drops to - it's 5 bars, which is, btw, the pressure that is created by the LPFP - it never goes below ~5 bars in the rail. Which tells me the LPFP is working fine. I did not have to pay them $1,200 to get to know that.
Buy WHY does the fuel pressure at the rail disappear in these specific conditions? I have been struggling with this for the past 7 months. I experienced this issue for the first time just after my 2 year warranty on the new engine block labour ended. Done by another authorized BMW service - Brian Jessel Vancouver - avoid that place like a plague. I was servicing my car there regularly until their negligence resulted in the need for a new engine block - timing chain assembly disintegrated completely and destroyed the engine.
Could the fuel pressure issue be in any way related to the engine block swap?

[Ondras]

Can someone please help or point me to someone who can?

[Ondras]

One more observation. I can replicate it very consistently - after a drive, engine at operating temp. I park it in the garage, let the engine run, coolant temp goes up, and when the cooling fan comes on at high speed it unsettle the idle and at that point the fuel pressure drops to 5 bar and engine dies, the LPFP pumps till the engine dies. So it's definitely not the LPFP causing the pressure drop. It's something sending wrong info to the ECU and ECU to the HPFP regulator. What could it be? Looks like it's related to the fan coming on and taking more electrical power.

[ChiltiCoatl89]

Been doing research, looked and searched and found reports of temperature related issues directly connected to LPFP, Also, how is your battery? You pretty much replaced everything except the LPFP at this point. have your battery checked, Is your car running any tunes?

[Ondras]

All stock, no tunes. Battery is new as well. Yesterday I reproduced the issue as well, the LPFP runs and sends fuel as pressure drops and engine dies. So it's not it. Something is telling the HPFP regulator to drop pressure.

[Ondras]

update -
I've changed the LPFP, OEM Pierburg. It seems to be fixed now, I cannot reproduce it in any of the situations the problem used to happen very consistently.
I am happy if that was it. However I am not able to explain it with any logic - if the pump was having issues, why only sometimes? Why it did not show any problems at acceleration, high revs, when the engine consumes most gas? Why only on idle when the engine was restarted from warm? It seems like when the cooling fan came on high speed and the coolant pump was working hard to cool the engine that was sitting turned off for a bit and oil and coolant temps were going above the normal due to the heat soak. but what does it have to do with the fuel pump that is sitting in the cold gas tank.

[ChiltiCoatl89]

BMWs can be confusing to diagnose sometimes, especially for people who buy into the brand, not knowing what they are getting into, this is not the case however, you did a great job and I did my best to give you the info in which I found as well, BMWs do love their nominal voltages on all their sensors and plugs and connections, I am not saying or implying that it was electrical related, it could be (mechanically) (or both), due to age, climate conditions, etc, When something goes out of whack, even for something small, (like Voltage readings) everything is intertwined to safeguard its proper functions, to prevent further damage. Since you owned the car, you've never had this issue prior correct until recently correct? Where do you store your car normally? I Definately respect your proactiveness in figuring it out especially on your own, props to you!

[Sahmeebuilt]

Originally Posted by Ondras

update -
I've changed the LPFP, OEM Pierburg. It seems to be fixed now, I cannot reproduce it in any of the situations the problem used to happen very consistently.
I am happy if that was it. However I am not able to explain it with any logic - if the pump was having issues, why only sometimes? Why it did not show any problems at acceleration, high revs, when the engine consumes most gas? Why only on idle when the engine was restarted from warm? It seems like when the cooling fan came on high speed and the coolant pump was working hard to cool the engine that was sitting turned off for a bit and oil and coolant temps were going above the normal due to the heat soak. but what does it have to do with the fuel pump that is sitting in the cold gas tank.

Was this the problem ? because i did the same as u. And i just ordered up the lpfp. I thought i was the only only one dealing with this problem. I would explain to everyone about this and they just looked at me funny. I would of never thought it would be the lpfp because even when cranking over on the stalls . U can hear the pump pumping. I took the seats of and even the fp cover .