# This is HPFP failure, right?



## TGrits10 (Nov 17, 2007)

Bear with me, I have a bunch of evidence but I want to be sure:

2015 650i GC (n63tu), after a brief wot started missing and nearly stalled at the next light, DTM/limp mode, miss goes away if revs stay up a bit (2k+).

Codes:
-P15DF - cold start fuel pressure too low
-P0087 - fuel rail/system pressure too low
-P0171 & P0174 - system too lean
-P0300 - Random/Multiple cylinder misfire
-P0301 & P0303 - cylinder 1 & 3 misfire

Seems pretty clear Bank 1 fuel pressure is down causing lean mix and missing, so what other things beside the hpfp could be to blame?


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## TGrits10 (Nov 17, 2007)

Update: I***8217;m retarded. Totally missed that P0174 is bank 2. This whole time I was thinking it was only bank 1. Not HPFP, but the low pressure pump in the gas tank, which I will be replacing this weekend, or maybe sooner depending when the part gets here. Sigh. If it***8217;d been HPFP like I thought, it would have been under warranty.


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## TGrits10 (Nov 17, 2007)

Update: 
LPFP went in pretty smoothly, probably 1-1.5 hours start to finish being methodical and not knowing what I was getting into. Happened to have filled up not long before this all happened, so shop rags to keep gasoline from going everywhere was a must. Hardest part was getting the small middle module back into its slot/clips. anyway...

It's worse now! Well, it got worse. First turned on the ignition for a while a couple times let it get primed, then fired it up and it seemed pretty happy. Still gave P15DF (cold start low fuel pressure), but I figured there would be some air to work out of the fuel lines, so I drove around aimlessly for a while. Previously I'd found that it would struggle at low rpms and therefore putting the trans in sport mode kept the revs up and prevented the missing. 

By the time I got back from the shakedown run, even that wasn't foolproof, AND it was backfiring like CRAZY off the throttle. Meanwhile throwing codes P0087 (system lean), P0300 (multiple/random misfires), and P0301/P0303 (misfire cyl 1 & 3). So...lean but backfiring like crazy? What the heck is going on here?


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## TGrits10 (Nov 17, 2007)

Update: LOL/FML
It was Bank 1 HPFP after all. Based on the info in the first post, I took it to the dealer to get a new HPFP under warranty, but they said they saw low fuel pressure on both high pressure banks, AND on the low pressure side of the system. This pointed squarely at the LPFP (in the gas tank), which they wanted $1400 to change out before they can look at anything else, so I cursed at my luck, ordered a pump ($355 @ FCP Euro + expedited shipping + tax)(price is now $464 for whatever reason), authored the 2nd post, paid the dealer the $100 diagnostic fee, and waited for the weekend to install the new pump and get my car back to normal.

Imagine my frustration when the pump install didn't change anything. At that point my car had been down for just over a week, I was out close to $500, and I still didn't even know what the problem was. Meanwhile I'm commandeering my wife's van to commute to work, so she's even more stuck at home with the kids. It's a nightmare. I have a lot of signs pointing to the starboard side HPFP, but I also have a few codes and the BMW service department pointing to the low pressure side. I've gotten everything I can from the internet and my OBD app, and if it's not HPFP then I have no idea. I don't want to bring it back to BMW for another round of expensive throwing of parts at a problem. But how else do I ultimately solve the problem?

So back it goes to the dealer. The SA is sympathetic to my plight, understands I've just thrown away $500 on a wild goose chase they led me on, assures me they'll get to the bottom of it this time. I'm still worried it'll be some obscure item not covered by warranty and the tally for this problem will continue to climb. But what can I do. At least I have a loaner so the wife has her car. 

Then the SA lets me know they solved it with a new Bank 1 HPFP and my car will be ready this afternoon. I don't know how to feel. Thank God it's over? Why did they flag the LPFP when it was fine? Why didn't I just buy an HPFP from FCP ($238) and pop it in, which would have been a week faster and $200 cheaper than this fiasco?

Anyway I can't edit the 1st post and that sucks because the conclusion is that all signs pointed to Bank 1 HPFP, it WAS Bank 1 HPFP, and BMW goofed and wasted $500 for me. I'm not bitter. I'm fine. I'm FINE.


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## dagoo98 (Apr 23, 2004)

TGrits10 said:


> Update: LOL/FML
> It was Bank 1 HPFP after all. Based on the info in the first post, I took it to the dealer to get a new HPFP under warranty, but they said they saw low fuel pressure on both high pressure banks, AND on the low pressure side of the system. This pointed squarely at the LPFP (in the gas tank), which they wanted $1400 to change out before they can look at anything else, so I cursed at my luck, ordered a pump ($355 @ FCP Euro + expedited shipping + tax)(price is now $464 for whatever reason), authored the 2nd post, paid the dealer the $100 diagnostic fee, and waited for the weekend to install the new pump and get my car back to normal.
> 
> Imagine my frustration when the pump install didn't change anything. At that point my car had been down for just over a week, I was out close to $500, and I still didn't even know what the problem was. Meanwhile I'm commandeering my wife's van to commute to work, so she's even more stuck at home with the kids. It's a nightmare. I have a lot of signs pointing to the starboard side HPFP, but I also have a few codes and the BMW service department pointing to the low pressure side. I've gotten everything I can from the internet and my OBD app, and if it's not HPFP then I have no idea. I don't want to bring it back to BMW for another round of expensive throwing of parts at a problem. But how else do I ultimately solve the problem?
> ...


This what happens when you go somewhere to diagnose the problem to then try and fix it yourself. You will almost certainly lose. How is it in all this dwelling on the past you've never considered that maybe both parts were bad?:eeps:


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## TGrits10 (Nov 17, 2007)

dagoo98 said:


> This what happens when you go somewhere to diagnose the problem to then try and fix it yourself. You will almost certainly lose.


To be fair, I diagnosed it and then went to the dealer to have it fixed because it was under warranty. Their own diagnostic process was supposed to be a formality.

They threw me a curveball by flagging the low-pressure side, and I was inclined to believe them because, you know, they're the official manufacturer's representatives with all the diagnostic tools and technical information and all that. In hindsight the symptoms did not match up with LPFP failure and I wish I'd pressed them to look deeper there before recommending a $1400 repair, or to look at the HPFP first, but why would they listen to me, a civilian with an OBD tool and a vested interest in targeting the warrantied part?



dagoo98 said:


> How is it in all this dwelling on the past you've never considered that maybe both parts were bad?:eeps:


Oh I have, but hahano. Theoretically possible. HIGHLY unlikely. LPFP's don't generate low pressure, they make full pressure or no pressure, unless perhaps the motor's bearings are going, which would cause a gradual onset of symptoms, not the sudden onset experienced. If there is low pressure it's more likely to be something else causing a restriction, like a clogged fuel filter or fuel line, etc.

It is possible-but-unlikely that the LPFP was a bit off in a way that does not cause any problems/symptoms (yet?) but would show up on BMW's diagnostics and be flagged for prophylactic replacement. In that case it would be clear that it is not the source of the symptoms, and the investigation should continue, no?

IF hypothetically (Bobs from Office Space: "And believe me, this is hypothetical!") the LPFP & HPFP both coincidentally failed at the same time, and the LPFP replacement was indeed necessary, one could at least expect some difference, some change in the symptoms, when it was replaced. Low-pressure-side real time fuel pressure readings were exactly the same before and after the LPFP changeout, as were symptoms and trouble codes.

Of course my curious mind wonders what their diagnostic tools would read from the low-pressure side now, with the symptoms absent and a shiny new LPFP in place. Would they still find low pressure? Or was it a fluke reading possibly caused by a fuel system in some kind of turmoil from the HPFP problem and engine start/stop/stumble action? Who knows.

If I could put the old LPFP pump back in and get my money back I would.


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## dagoo98 (Apr 23, 2004)

TGrits10 said:


> To be fair, I diagnosed it and then went to the dealer to have it fixed because it was under warranty. Their own diagnostic process was supposed to be a formality.
> 
> Oh I have, but hahano. Theoretically possible. HIGHLY unlikely. LPFP's don't generate low pressure, they make full pressure or no pressure, unless perhaps the motor's bearings are going, which would cause a gradual onset of symptoms, not the sudden onset experienced. If there is low pressure it's more likely to be something else causing a restriction, like a clogged fuel filter or fuel line, etc.


Are you actually saying that a fuel PUMP does not generate pressure? If so, why are there fuel pressure gauges and specs for fuel pressure parameters for every combustion engine known to man?......To diagnose clogged fuel filters? For someone who appears so knowledgeable, you've never replaced a conventional fuel pump and had it remedy a low fuel pressure problem? I'm confused.


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## Doug Huffman (Apr 25, 2015)

A benefit of paying the dealership to do a work order is their acceptance of liability for the diagnosis and goodworkmanship of the repair.


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## TGrits10 (Nov 17, 2007)

dagoo98 said:


> Are you actually saying that a fuel PUMP does not generate pressure? If so, why are there fuel pressure gauges and specs for fuel pressure parameters for every combustion engine known to man?......To diagnose clogged fuel filters? For someone who appears so knowledgeable, you've never replaced a conventional fuel pump and had it remedy a low fuel pressure problem? I'm confused.


No I'm not saying that. What I'm saying is that generally (admittedly it's a generalization) when the LPFP has a problem, it's a problem of not running when it's supposed to be running, as opposed to a problem of not running well enough. It's a simple device designed to run continuously at a single speed, and it's pretty much running or not. Any number of things can cause it to not run when it's supposed to, but if it's not running, neither is the engine.

IF something in the low-pressure side of the fuel system was causing lower-than-design but higher-than-zero pressure, the engine could run poorly, or maybe even run just fine if the lower pressure remains within design tolerances and/or safety factors. We never did rule out everything in the low-pressure side and give it a clean bill of health - but we know that if something's not right in there, it's not causing any symptoms or DTCs at this time. :dunno::eeps:

The point, in any case, is that the LPFP was singled out by the dealer tech as most likely to be the cause of low pressure, and in hindsight that doesn't sit right with my understanding of fuel systems. They found low pressure upstream of the HPFP so it made sense to look upstream for the problem, but the problem and the part they zeroed in on don't match.

Unless of course BMW knows their fuel systems better than I do and their LPFPs do experience partial failure and therefore their diagnostic procedure tells them to target the LPFP in such a case. Which is why I'm not up in arms demanding an apology or whatever.

I don't know what the correct/design low-side fuel pressure is for this engine, but I do know that the pressure was the same before and after the LPFP changeout, therefore that part was not a/the problem. Beyond that...can't be sure of much.


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## dagoo98 (Apr 23, 2004)

TGrits10 said:


> No I'm not saying that. What I'm saying is that generally (admittedly it's a generalization) when the LPFP has a problem, it's a problem of not running when it's supposed to be running, as opposed to a problem of not running well enough. It's a simple device designed to run continuously at a single speed, and it's pretty much running or not. Any number of things can cause it to not run when it's supposed to, but if it's not running, neither is the engine.
> 
> IF something in the low-pressure side of the fuel system was causing lower-than-design but higher-than-zero pressure, the engine could run poorly, or maybe even run just fine if the lower pressure remains within design tolerances and/or safety factors. We never did rule out everything in the low-pressure side and give it a clean bill of health - but we know that if something's not right in there, it's not causing any symptoms or DTCs at this time. :dunno::eeps:
> 
> ...


A key determination on the low pressure side of any fuel system is the difference between pressure and volume. You can have good fuel pressure and low volume. In any case, it is the industry standard whether at the dealer or elsewhere that you remedy all faults on the low side before you can properly diagnose the high side. A good tech will not and should not bypass low side faults and continue to diagnose the high side because he could be spinning his wheels for no reason.


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## dagoo98 (Apr 23, 2004)

Doug Huffman said:


> A benefit of paying the dealership to do a work order is their acceptance of liability for the diagnosis and goodworkmanship of the repair.


My point exactly, if you decide you are going to do the work on your own this is the risk you take and your complaints will fall on deaf ears because they did not do the work and you decided to accept the liability of the outcome of the repair.


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## TGrits10 (Nov 17, 2007)

dagoo98 said:


> A key determination on the low pressure side of any fuel system is the difference between pressure and volume. You can have good fuel pressure and low volume. In any case, it is the industry standard whether at the dealer or elsewhere that you remedy all faults on the low side before you can properly diagnose the high side. A good tech will not and should not bypass low side faults and continue to diagnose the high side because he could be spinning his wheels for no reason.


Yeah no I'm with you on them wanting to address the low side if there's a problem there, I think what I'm leaning toward but not wanting to outright accuse them of is lazy/incomplete diagnostic effort. I'm only leaning because I don't know what kind of procedures and layers they're bound to, and I don't know how deep it's reasonable to expect them to look for the $100 initial inspection.

Maybe it's dumb to expect them to run checks on low-pressure side components when for $100 they're gonna have like half an hour with the car, tops. In that case maybe it makes sense to say "I dunno, try replacing the fuel pump and see if that solves it :dunno:. BTW that'd be $1400 that you're on the hook for whether it's actually faulty or not. Sign here please :thumbup:." Is it just me or does that smack of throwing parts at the problem at the customer's expense rather than actually tracking down the problem?

Let me phrase it this way: If this occurred under the original bumper-to-bumper factory warranty, what would they have done when they got the low-pressure side fault? If their diagnostic/troubleshooting procedures dictate that the next step is to run no further checks, replace the LPFP at BMW's expense, and go from there, then I can't reasonably have a problem with what they presented to me. Buuuut I have a hard time believing that the correct response to "We have an out-of-spec parameter" is "Let's not investigate any further, no, data is for pussies, let's just replace the most expensive component in that system and hope it works."

Like, "we found a fault in the low-pressure side, but we can't dig deeper without charging you for more diagnostic time, what do you want to do?" is one thing. "We found a fault in the low-pressure side, and we refuse to dig deeper until a new LPFP is installed." is quite another.


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## TGrits10 (Nov 17, 2007)

dagoo98 said:


> My point exactly, if you decide you are going to do the work on your own this is the risk you take and your complaints will fall on deaf ears because they did not do the work and you decided to accept the liability of the outcome of the repair.


Are you saying BMW would waive payment for the LPFP if I agreed to have them replace it and it didn't solve the problem? That is not what was presented to me, and not how the World works, in my experience.


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## TGrits10 (Nov 17, 2007)

Update: The other HPFP went down, dealership again made a mess of it, at least this time I didn't have to throw away $500. At what point do I call out the dealer by name so the world can know their techs are useless?

Short version: 
Bank 2 HPFP failed, and I (thanks in part to my ordeal with Bank 1 HPFP above) quickly diagnosed the problem and brought the car to my local dealer for warranty replacement. Dealer tech instead flagged fuel pressure sensor, so I ultimately authorized $642 labor to swap the pumps, pump swap proved HPFP, Final bill $0, downtime 6 days.

Long version:
Just like with Bank 1, hard acceleration with pop/lurch at lift-off, drivetrain malfunction, limp mode, keeping rpm up helps the fuel pressure stay up. Happened to occur as I was heading out to an important meeting an hour away, so I put 2 hours on the engine with the behavior gradually degrading before I could get it to the dealer. Checked the codes before I headed back from the meeting, as expected low fuel pressure Bank 2, misses cyls 5 & 6, etc., so I called the dealer from the road requesting to get the car admitted asap, they gave me a slot a few hours out so I parked the car strategically at the office (and still had trouble getting it going when it was time to hop over to the dealer).

At the dealer, I let the SA (same guy I dealt with last time, but that was almost a year ago so I doubt he remembered) know it was HPFP, described behavior & codes, reminded them of the ordeal they put me through last time, and left hoping it would go better this time around. It was Friday afternoon and they couldn't promise they'd get to my car until middle of next week, but they always give you a loaner no matter what, so at least I have a car to drive. So far so good.

Wednesday afternoon I get the text: 'bad fuel pressure sensor Bank 2, $1100, proceed?' I take a little time to think it through, trying to line up a failed sensor with the symptoms, and ultimately it makes no sense, outside of the sensor happening to fail at the exact same time as something else, that something else being, almost certainly, the HPFP. So a contentious text exchange and a couple phone calls later, the situation is laid bare: the sensor is reading no pressure whether in the fuel rail or reading atmospheric, so it must be bad, and the tech cannot/will not look further until the sensor is resolved. They don't necessarily not believe me that the HPFP has failed, but they cannot dig any farther in that direction unless I specifically direct it at my expense, which to swap the pumps would be $642. If it turns out to be the HPFP, all costs will go into the warranty bucket and I pay nothing. If it doesn't prove HPFP, I'm on the hook for everything. Orrrr I could cut my losses, pay the $100 diagnostic fee, order the HPFP for $2xx, figure out transportation for Thursday and Friday somehow, and install the pump on Saturday. I'm like 99.5% sure it's the HPFP, if we can just prove that to BMW....I compared it to a poker game: I've got 4 aces, but the other guy just put in a HUGE raise. What's he got? 

So Thursday morning I finally, reluctantly, said yeah go ahead with the swap, and sweated it hard. Time passed at a snail's pace. I was on edge and grumpy, certain I'd thrown away several hundred dollars on a dream of BMW honoring their promises. 

Thursday afternoon, the SA called to tell me the car was fixed, I owe $0, yadda yadda yadda. Hallelujah. Relief beyond description. Picked up the car a couple hours later, freshly detailed, all is right with the World again. No word on the status of that sensor. Presumably it repaired itself.


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## TGrits10 (Nov 17, 2007)

An interesting development that I've been holding off on mentioning in case it was temporary:

The tendency to stumble/stall under certain circumstances following cold starts has completely evaporated. Also, the rough idle has not entirely cleared, but it is significantly improved. Specifically:
-Cold start, car parked facing uphill in gently sloped driveway, back down to bottom of driveway, shift to Drive to pull up to other side of driveway, engine stalls. Used to be reliable as gravity, now cannot make it happen. I've tried.
-Cold start, car parked uphill in gently sloped driveway or parking space, shift to Reverse, engine stumbles, coughs, recovers with emphatic revs, tries to play it off but we all saw. Used to happen more often than not, has not happened since the 2nd HPFP was replaced.
-Rough idle when warm, strong enough to send surges through the transmission and shake the car, such that I would shift to Park at long lights. Now there is a mildly annoying shaking that I feel through my seat but passengers don't, doesn't transmit to transmission.

I replaced the plugs & coils, ran fuel injector cleaner through, ran fuel system cleaner through, and eventually gave up since swapping the injectors was too big-ticket for something was merely annoying. Then it got solved by something unexpected. Nice to be reminded that I don't always know everything.

So anyway, that's cool. Seems to me the HPFP was likely not at 100% the entire time I've had the car, and causing what I eventually wrote off as irritating-but-normal N63tu behavior. Turns out maybe it's not so much normal, but widespread? Now I'm curious how many N63s out there could benefit from new HPFPs even if they aren't clearly failing.


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