N43 Fuel Pressure Issues

zEDo · 07-04-2022, 04:01 PM

Hi everyone,

So I'm down this mad rabbit hole of chasing a missing injector adaptation/lernbit on my 2011 e90 320i with n43b20 170ps.
Long story short I think I narrowed it down to the Fuel Preparation System.

First of all my Low Pressure circuit fluctuates a bit out of spec. I believe ISTA+ specs the jitter of the circuit to 5bar +/- 0.2 bar which is quite liberal from what I've read in most places. I believe Bimmerprofs specs tolerances in +/- 0.1bar. My jitter at it's worst is almost +/- 0.3 bar.

Secondly my High Pressure circuit/rail is stuck at 150bar all the time, sometimes it rises a bit, most I've seen it rise since I started tracking it is 170bar. Bimmerprofs specs the HP circuit to rise from 150bar to 200bar from 2000rpm onwards. The jitter is within spec, I've never seen it rise or fall more than 0.08 bar.

Third of all, when shutting off the engine, BOTH HP and LP segments rise in pressure continuously for about 8 minutes(HP rises from 150bar to 238bar and LP rises from 5bar to 5.6bar) and then the slowly decrease.

A couple more things worth mentioning are that 2 or 3 times in the past 6 months I've had the engine randomly shut off when coming to a normal dead stop. No fault codes registered, I turned the engine back on after without any issues. The other thing is that sometimes I feel a feint smell of gas when starting the car. No smoke coming from the back.

Any help is much appreciated.

Cheers.

cheerio · 07-05-2022, 07:44 PM

You might have better luck posting in the N54 forum, as the N43 wasn’t sold in the US and many other parts of the world.

0l0dom0l0 · 07-06-2022, 09:17 AM

Replaced the low and high pressure sensors?

zEDo · 07-12-2022, 04:27 AM

Thanks for the tips.
I'm planning on replacing both sensors preventively to see if that solves the issue as it is cheaper than buying a pressure test kit.
I'll post the results once I replace them. If that doesn't work next I will replace the fuel pressure regulator/filter. Do you guys recommend any AM sensors or just to stick with OE?

zEDo · 03-10-2023, 02:26 AM

Resurrecting this thread to update you on the issue.

After an insane amount of hours researching this issue I have found out the culprit: it was the leaking vacuum pump. Took it off the engine, it was filled with oil, cleaned it, changed out all its gaskets with viton ones from a uk seller on ebay(parts not available from bmw). It was one of the most infuriating jobs because the pump is held in by 3 blind bolts at the back of the engine.
After I did this job pretty much all the issues went away: I got rock solid idle, fuel consumption dropped down(prolly due to disa working properly), throttle response in 1500-2000 range is like a hair trigger and no more oil leak/loss and the fuel pressure chart is much more consistent now.
Also I took this oportunity to check all my injectors and I'm lucky that the previous owner put in full index 11 :> . All these issues for 3 bloody o-rings.

Cheers.

07-04-2022, 04:01 PM	#1
zEDo New Member 0 Rep 9 Posts Drives: E90 320i LCI Join Date: May 2022 Location: Romania iTrader: (0)	N43 Fuel Pressure Issues Hi everyone, So I'm down this mad rabbit hole of chasing a missing injector adaptation/lernbit on my 2011 e90 320i with n43b20 170ps. Long story short I think I narrowed it down to the Fuel Preparation System. First of all my Low Pressure circuit fluctuates a bit out of spec. I believe ISTA+ specs the jitter of the circuit to 5bar +/- 0.2 bar which is quite liberal from what I've read in most places. I believe Bimmerprofs specs tolerances in +/- 0.1bar. My jitter at it's worst is almost +/- 0.3 bar. Secondly my High Pressure circuit/rail is stuck at 150bar all the time, sometimes it rises a bit, most I've seen it rise since I started tracking it is 170bar. Bimmerprofs specs the HP circuit to rise from 150bar to 200bar from 2000rpm onwards. The jitter is within spec, I've never seen it rise or fall more than 0.08 bar. Third of all, when shutting off the engine, BOTH HP and LP segments rise in pressure continuously for about 8 minutes(HP rises from 150bar to 238bar and LP rises from 5bar to 5.6bar) and then the slowly decrease. A couple more things worth mentioning are that 2 or 3 times in the past 6 months I've had the engine randomly shut off when coming to a normal dead stop. No fault codes registered, I turned the engine back on after without any issues. The other thing is that sometimes I feel a feint smell of gas when starting the car. No smoke coming from the back. Any help is much appreciated. Cheers. Attached Images
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07-05-2022, 07:44 PM	#2
cheerio Private First Class 144 Rep 149 Posts Drives: E61 + E36 + E90 scrapheap Join Date: Mar 2021 Location: Melbourne iTrader: (0)	You might have better luck posting in the N54 forum, as the N43 wasn’t sold in the US and many other parts of the world.
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07-06-2022, 09:17 AM	#3
0l0dom0l0 First Lieutenant 69 Rep 316 Posts Drives: BMW E92 330i Join Date: Jun 2020 Location: Uk iTrader: (0)	Replaced the low and high pressure sensors?
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07-12-2022, 04:27 AM	#4
zEDo New Member 0 Rep 9 Posts Drives: E90 320i LCI Join Date: May 2022 Location: Romania iTrader: (0)	Thanks for the tips. I'm planning on replacing both sensors preventively to see if that solves the issue as it is cheaper than buying a pressure test kit. I'll post the results once I replace them. If that doesn't work next I will replace the fuel pressure regulator/filter. Do you guys recommend any AM sensors or just to stick with OE?
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03-10-2023, 02:26 AM	#5
zEDo New Member 0 Rep 9 Posts Drives: E90 320i LCI Join Date: May 2022 Location: Romania iTrader: (0)	Resurrecting this thread to update you on the issue. After an insane amount of hours researching this issue I have found out the culprit: it was the leaking vacuum pump. Took it off the engine, it was filled with oil, cleaned it, changed out all its gaskets with viton ones from a uk seller on ebay(parts not available from bmw). It was one of the most infuriating jobs because the pump is held in by 3 blind bolts at the back of the engine. After I did this job pretty much all the issues went away: I got rock solid idle, fuel consumption dropped down(prolly due to disa working properly), throttle response in 1500-2000 range is like a hair trigger and no more oil leak/loss and the fuel pressure chart is much more consistent now. Also I took this oportunity to check all my injectors and I'm lucky that the previous owner put in full index 11 :> . All these issues for 3 bloody o-rings. Cheers.
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