[aupshon]

Hi All,

Long time lurker trying to diagnose my recently acquired N53 without replacing the entire thing.

Car: 325i E91 131k miles manual. Good MPG 40mpg + driving at 80mph CC
Recalls: All done, Index 11 injectors HPFP replaced in 2014
Replaced: Plugs and coils
Issues: Half check engine light under heavy load/hard acceleration Nox codes

Behaviour: The cars cold starts can be a bit noisy, slight ticking noise but idle is stable overrall. Noise goes away once warm

If I drive fairly gently I can rev the car out and get some okay performance, any excessive load on the car such as cruise control up a hill or low rpm half throttle I get a big jerk as though someone has hit the brakes quickly and a half check engine light. Once the light is on the car idles and drives terribly. It wont even maintain 70mph up a hill with CC. Idle up and down. I have to reset everything to get fairly normal performance.

There is what feels like a slight torque change/misfire/jerkiness when accelerating gently from lowish rpm (2000rpm up).

I have run through various INPA checks and have been researching bimmerprofs info. My biggest concern I don't want to replace things for the sake of it.

Bimmerprofs say I need to fix Noxem issue FIRST before anything else but my research seems to say that A) Nox issues wont cause performance issues apart from bad mileage - is this correct? B) bad injectors will foul a new sensor

Why should I replace a £400 sensor, only to potentially then replace £1k+ injectors, which might have damaged the initial £400 sensor, leading to yet another replacement?

There also seems to be the possibility of buying the probe and splicing that into the Nox circuit. Has anyone done this?

HPFP - https://bimmerprofs.com/n43n53-fuel-supply/

The above link explains the fuel system. I have revved my car to 6500rpm at idle and my HPFP drops to 150 then 90bar as it nears 6500rpm.

Has anyone experienced similar issues or managed a diagnosis route.

[0l0dom0l0]

You need to post exactly what codes you have for me to be able to help you.

It does sound like an issue with your HPFP. All but the very last revision of the part are prone to failure.

[aupshon]

Originally Posted by 0l0dom0l0

You need to post exactly what codes you have for me to be able to help you.

It does sound like an issue with your HPFP. All but the very last revision of the part are prone to failure.

Oh silly me I thought I had. Here is a screenshot from ISTA.

Ugh I really hope it isn't as BMW wants £1007 for the pump! I just purchased a Nox em so at least those codes will be sorted now.

I can provide the video of ISTA and fuel pressure when revving.

[0l0dom0l0]

Have you cleared the codes and is that what comes back?
You have the dreaded HPFP code there, does seem likely that your HPFP is on the way out.

[aupshon]

Originally Posted by 0l0dom0l0

Have you cleared the codes and is that what comes back?
You have the dreaded HPFP code there, does seem likely that your HPFP is on the way out.

I have cleared them and the only one that comes back is the Nox sensor. The mixture one seemed to be from an injector cleaner I added.

Will the nox sensor create the issue I’m experiencing? Or is it more fuel/injector related

What are my options with the HPFP? Remanufactured options available or am I stuck with the dealer?

[0l0dom0l0]

I think it's your HPFP.

Options are the dealer only really. The pumps they sell are all remanufactured units to the latest revision.

Hauber.de have them for 800 euros.

With that, the NOx sensor, and the index 11 injectors you should be sorted. That's all 3 N53 weaknesses sorted.

[aupshon]

Originally Posted by 0l0dom0l0

I think it's your HPFP.

Options are the dealer only really. The pumps they sell are all remanufactured units to the latest revision.

Hauber.de have them for 800 euros.

With that, the NOx sensor, and the index 11 injectors you should be sorted. That's all 3 N53 weaknesses sorted.

I managed to find a decent price from BMW costswolds, will check on hauber because i'm not sure what the import duties will be.

Still waiting on Noxem. Once that's installed will get HPFP and update once both are up and running.

[aupshon]

Just to give an update for anyone else with the N53.

I'm making headway slowly before pulling the trigger on the HPFP.

So I have recently put all new plugs and 50% new coils (only oily ones I replaced). I have done around 1000-1500 miles on the car all long distance. I let the car sit overnight, pulled the plugs, each one was perfectly dry although quite white. I think I can safely say I do not have an injector issue but an fueling issue although i already knew that.

I bought an amazon fuel tester kit which didn't work so ended up getting a new LPFP sensor and new seals for the vanos solenoids as it was the same price and less messing around . I have changed the LPFP sensor (removing the intake mani is a real pain. I've done a couple short trips in the car, no change really but I have noticed the HPFP is reading 150 bar now, although the car was not fully warmed up.

I am going to reset all fuel adaptations and go for a long run to see if anything is different.

Upon slightly revving the car and playing with the throttle the lpfp does dip to 3bar now and then. So it does seem to be pointing to my LPFP but I have not come across ANY posts relating to it being replaced, it seems even BMW will replace the HPFP before that. Why would I be getting these readings though?

I still get the weird torque surge from low rpm. A little throttle and the torque comes but instantly backs off. Vanos solenoid cleaning and new seals hopefully will eliminate that as a cause.

On a 280 mile round trip with maybe 50 miles in london I got 37mpg which seems okay. Clearly the Nox em isn't doing anything until the fuel issue is sorted.

[aupshon]

So I just did two trips this evening around 60 miles each and managed to do some logging on INPA while I was driving and experience the issues. INPA refreshes every second so I will list my throttle position, LPFP and HPFP.

After looking at the videos I cannot really seem to find a pattern. There is very clearly a fuel issue but whether it’s the Low or High isn’t very clear. The low sensor gives a weird 7-9 bar reading with an exclamation mark and the HPFP goes all the way down to 90 bar in some instances. It looks like I’ll need to replace both possibly. I have written out below a couple of videos and will upload them for you guys to check out.

In order it’ll be Throttle, LPFP(bar), HPFP (bar)

39% | 47% | 49% | 49% | 49% | 11% | 0%
4.9 | 4.0 | 5.8 | 6.4 | !9.3 | 3.7 | 5.1
199 | 166 | 131 | 129 | 130 | 147 | 238

33% | 47% | 49% | 46% | 39% | 75% | 75% | 75%
4.9 | 5.2 | 6.5 | 2.5 | 4.1 | 4.1 | 5.9 | 1.7
200 | 180 | 135 | 121 | 132 | 110 | 102 | 105

[Schomosport]

Bought 530i in July. Went straight into shop to fix aircon fault, first drive afterwards, engine light came on under heavy load, 29F2 HPFP and 30DE NOX correlation faults. Much investigation and several HPFP rebuilds since, I am a couple of hundred miles into a successful pump fix (but very early days), NOX fault remains. No hurry to replace expensive NOX since I suspect the simoultaneous arrival of the two faults in the first place may mean the HPFP fault has caused the NOX fault. HPFP switches to LPFP when light comes on and you can still do motorway speeds easily in that condition. I.e. excessive running with the engine light on may have casued me to kill the NOX sensor if it was running rich. But who knows, they seem to be an expensive and ureliable item, the invoice records for both my 525i and my 530i show they have been changed on both cars.

Tips:
INPA - every time you check for faults, before clearing them download the freezeframe data. If the HPFP is failing it will record the drop-out pressure, km, rpm, km\h, airmass sensor. Build up a picture of your HPFP failures to help you understand what is going on.
TestO - been playing with TestO this week. TestO is datalogger software and will log your choice of DME data points via the OBD port. With 12 parameters selected it logs at about 20Hz which is much better update rate than INPA. So for instance you can log both fuel pump pressures and rpm and speed etc. If you have an INPA set up, or perhaps more correctly a working EDIABAS set-up, then TestO worked for me almost straight away, all I did was change the COM port setting in the .ini. Will post some logs over the next couple of days as keen to 'prove' to myself my HPFP repair is working, need it to take me to NW Scotland in May. Links to TestO can be found through this site / Google.

[aupshon]

Did you rebuild the HPFP yourself or get a shop to? I've looked into this and it seems fairly simple as the seals fail and you just need to ensure that there's no air in the pump whatsoever during reassembly. I may have a go on my old one once I've replaced it but I don't have the time to let the car sit idle while I mess around.

I believe by disconnecting the HPFP (electric connector) we can monitor the LPFP and if that maintains the 5 bar then it confirms an HPFP fault.

Depending on your MPG your NOx may be okay. I was getting 40mpg on long runs with the car and haven't seen the full capability yet as I won't run in stratified mode until all fuel errors are clear. I have seen that you can possibly clean the Nox sensor by soaking it in injector cleaner. Some has ultrasonic cleaned them but I believe the sensors might be too fragile for that. Another thing to play with on the old one.

I'll take a look at the codes and that software listed, 20hz seems brilliant!

I'll post my findings once I've disconnected my HPFP and checked pressure of LPFP but all signs so far are pointing to a new one which i'll only be able to fit after Christmas.

[Schomosport]

Overhauled the pump myself based on Youtube video by 'Afeef'.

Took several tries. I depart from some of his methods and the sizes of seals in the descriptions cannot be relied on. I plan a full write up of what I did but it won't be until I have put some sensible miles on it and can claim some level of reliability. I used BS019 viton o-rings shore harness 70. The quadrings didn't work for me, they are a bit chunkier and material got shaved off during assembly. I used CHF 11S poweer steering fluid.

Plot below compares HPFP and LPFP over 20 minute drive for 90k miles 525i believed to be on its original pumps and 530i with rebuilt pump. More jitter and variation on the rebuilt pump, note its a dynamic system so big changes in fuel demand will cause transients at both the high and low pressure sensors. The big drop on the 530i (brown) was 'charge past, drop back in and big lift for roundabout' overtake. Some similar drops also evident in the 525i trace.

[Schomosport]

8 parameters 20Hz
11 parameters 16Hz
20 minutes is about one Mb so no issues over file sizes

[aupshon]

Ah yes that's the same video I've been watching. It doesn't seem too difficult and a win if these can be rebuilt to last similarly as long as originals. Even if its 50% that's much better than forking out £800 for the same thing to happen in 70-100k miles.

Your graphs look considerably better than my figures despite getting the same error. My HPFP would drop to 90 bar in some instances although I am at 130k miles.

Would you say the reassembly is the hardest part or sourcing correct rings? Did you reassemble fully submerged to avoid airlock? Any special tools needed or made to complete the pump rebuild?

[Schomosport]

BMW are said to have tried 4 different types/sizes of O-rings. I don't know if the O-ring groove design changed. Size BS019 20.35 ID 1.78 THICK was the best match I could find after having measured up the groove dimensions and checked them with an online O ring design calculator. Oil generously when assembling and you will feel them pop into place as you screw down the lock rings. The ones I took out of my pumps were thinner, about 1.6. The heavier quadrings I tried required a lot of pressure to screw them in, felt wrong and the resulting damaged rings confirmed it. If you can't get the bellows out, unscrew the locking rings halfway, refit the solnoid, plug the fuel outlet and apply an airline to the fuel inlet. You should hear them pop, might take a 100 psi. Doesn't seem to have had any ill effects on the pump internals. Some people change all the solenoid o-rings, I haven't.

You need to change the oil seal behind the driving dog. 22 OD x 12 ID x 7 THK. You will probably end up with a standard seal, the pump uses what looks to be a special with a much wider lip. How/where you would get a replacement I don't know. The seal also wears grooves in the shaft, I used an SKF speedisleeve to reclaim it. About £30 and some careful measurement is needed to make sure the sleeve is in line with the lip of the seal since the sleeve is quite short. The seal fits in a parallel hole with no bottoming lip so you need to take care to push it down square, it needs to be down 7.0mm from the top. I had a little tool made up, to press it in with, cost a tenner, I can tell you where to get one.

You will need to hold the pump tightly in the vice to undo the peg rings. Take the solenoid off and set it aside if it gets in the way. I made a pair of special jaws up shaped to fit, took me half a day. The peg rings are 4 x 5mm holes on 20mm PCD (I think). I drilled and tapped a piece of scrap alloy plate with 4 M4 cap screws and they were man enough to undo them even after a bit of filing to cover for my drilling inaccuracies. Needs a couple of clonks with a lump hammer to shift them.

You also need a good wallop to undo the driving dog from the swash plate (pendulum). Hold dog in vice and punch and lump hammer in the oval recess. Ugly but deep breath and it works.

The thermal compensator allows for expansion and contraction of the oil with temperature. Its working range measured through the hole in the end with a vernier down to the spring loaded diaphragm is 27mm to 12mm (coilbound). Using CHF 11S, the compensator moves about 0.9mm per 10C change in temperarture. So you need to preset the compensator to give the pump some headroom to work down to the lowest temperature it might see (-30C?) while leaving enough travel in the other direction for the maximum under bonnet temperature the pump might see (120C?). I set mine to about 22mm at 20C. This aligns with a BMW Mini thread statement that a new Mini pump which uses a similar compensator is 19mm measured from the bottom of the depression or 22mm from the end. Right or wrong, who knows, nothing in ISTA on this for N53. To be able to preset the diaphragm, epoxy a length of 6mm tubing into the compensator hole and attach a 50ml syring to suck the diaphragm up (it's quite robust, it gets called a diaphragm but it is metal and more like a piston). Lock the syringe off by jamming it with a piece of wood. Proof your work over night to make sure it isn't leaking (pricker down the oil hole to recheck diaphragm position).

Filling: prefill the compensator via the oil hole and prime the three plungers. Activate them and try to get all of the air out. In this weather, warming the oil up helps a lot. You will need the pricker down the hole to the compensator becasue it air locks very easily, you can see the air bubble, it doesn't come out paticularly easily of its own accord so pop it, then carefully drip some more oil in until it locks again. Compensator is going to have a few cc oil sat on it, can easily take you half an hour or more. Assemble the dome to the pump without the oil seal or driving dog. Fill remainder of pump with oil, patiently allowing for the air bubbles to come out. Screw an M8 capscrew into the drive shaft with a locknut so you can get it undone again i.e. don't bottom it in its hole or you will have to dismantle the pump again to undo the screw. Rotate the pump back and forth, first with an allen key, then with an electric drill. Don't spin it too fast or you will turn the oil into a foam which just takes longer to get rid of the bubbles again. Allow a good couple of hours, do thirty minutes and go and watch some TV or something then do it some more.

Nearly done. Make sure the oil level in the pump is a few mm higher than the seal position so that when you push the seal in it doesn't trap air. I used retainer because the seal is not a particularly tight fit although its effectiveness is questionable since everything is covered in oil.

Remove the syringe that was sucking on the temperature compensator diaphragm and the pipe (hot air gun softens Araldite quickly). Measure the position of the compensator diaphragm. If you got the vacuum right then it will be too near the end and there is a risk of ejecting the oil seal when the pump is hot (been there, done that). Put the pump in the vice and undo two of the three torx screws holding the dome down about 1/2 turn. Slowly (slowly) release the third torx screw a until a small amount of oil leaks from the pump. Tighten everything down and measure the diaphragm position. Repeat until the diaphragm position is where you want it to be (22mm from end is my setting). Final tighten the torx screws. Refit solenoid and screw in drive dog finger tight (it will self tighten in use) and you are done.

I have spent a long time on this, no guarrantee it will work for any length of time or there aren't better methods, its a voyage of discovery. I have the luxury of retirement and another car so project work doesn't bother me athough I do hate taking the inlet manifold on and off, there just doesn't seem to be quite the right anount of space.

Good luck, any questions fire away.

[Schomosport]

Repair didn't work unfortunately.

Did a quiet 600 miles but first time I gave it some moderate stick - 40% throttle, M2 to 7000rpm and leaving the box to upshift blew the pump.

That's two repair attempts and one Ebay cheapie pump Since SEptember, time to buy a proper BMW one.

Originally Posted by Schomosport

BMW are said to have tried 4 different types/sizes of O-rings. I don't know if the O-ring groove design changed. Size BS019 20.35 ID 1.78 THICK was the best match I could find after having measured up the groove dimensions and checked them with an online O ring design calculator. Oil generously when assembling and you will feel them pop into place as you screw down the lock rings. The ones I took out of my pumps were thinner, about 1.6. The heavier quadrings I tried required a lot of pressure to screw them in, felt wrong and the resulting damaged rings confirmed it. If you can't get the bellows out, unscrew the locking rings halfway, refit the solnoid, plug the fuel outlet and apply an airline to the fuel inlet. You should hear them pop, might take a 100 psi. Doesn't seem to have had any ill effects on the pump internals. Some people change all the solenoid o-rings, I haven't.

You need to change the oil seal behind the driving dog. 22 OD x 12 ID x 7 THK. You will probably end up with a standard seal, the pump uses what looks to be a special with a much wider lip. How/where you would get a replacement I don't know. The seal also wears grooves in the shaft, I used an SKF speedisleeve to reclaim it. About £30 and some careful measurement is needed to make sure the sleeve is in line with the lip of the seal since the sleeve is quite short. The seal fits in a parallel hole with no bottoming lip so you need to take care to push it down square, it needs to be down 7.0mm from the top. I had a little tool made up, to press it in with, cost a tenner, I can tell you where to get one.

You will need to hold the pump tightly in the vice to undo the peg rings. Take the solenoid off and set it aside if it gets in the way. I made a pair of special jaws up shaped to fit, took me half a day. The peg rings are 4 x 5mm holes on 20mm PCD (I think). I drilled and tapped a piece of scrap alloy plate with 4 M4 cap screws and they were man enough to undo them even after a bit of filing to cover for my drilling inaccuracies. Needs a couple of clonks with a lump hammer to shift them.

You also need a good wallop to undo the driving dog from the swash plate (pendulum). Hold dog in vice and punch and lump hammer in the oval recess. Ugly but deep breath and it works.

The thermal compensator allows for expansion and contraction of the oil with temperature. Its working range measured through the hole in the end with a vernier down to the spring loaded diaphragm is 27mm to 12mm (coilbound). Using CHF 11S, the compensator moves about 0.9mm per 10C change in temperarture. So you need to preset the compensator to give the pump some headroom to work down to the lowest temperature it might see (-30C?) while leaving enough travel in the other direction for the maximum under bonnet temperature the pump might see (120C?). I set mine to about 22mm at 20C. This aligns with a BMW Mini thread statement that a new Mini pump which uses a similar compensator is 19mm measured from the bottom of the depression or 22mm from the end. Right or wrong, who knows, nothing in ISTA on this for N53. To be able to preset the diaphragm, epoxy a length of 6mm tubing into the compensator hole and attach a 50ml syring to suck the diaphragm up (it's quite robust, it gets called a diaphragm but it is metal and more like a piston). Lock the syringe off by jamming it with a piece of wood. Proof your work over night to make sure it isn't leaking (pricker down the oil hole to recheck diaphragm position).

Filling: prefill the compensator via the oil hole and prime the three plungers. Activate them and try to get all of the air out. In this weather, warming the oil up helps a lot. You will need the pricker down the hole to the compensator becasue it air locks very easily, you can see the air bubble, it doesn't come out paticularly easily of its own accord so pop it, then carefully drip some more oil in until it locks again. Compensator is going to have a few cc oil sat on it, can easily take you half an hour or more. Assemble the dome to the pump without the oil seal or driving dog. Fill remainder of pump with oil, patiently allowing for the air bubbles to come out. Screw an M8 capscrew into the drive shaft with a locknut so you can get it undone again i.e. don't bottom it in its hole or you will have to dismantle the pump again to undo the screw. Rotate the pump back and forth, first with an allen key, then with an electric drill. Don't spin it too fast or you will turn the oil into a foam which just takes longer to get rid of the bubbles again. Allow a good couple of hours, do thirty minutes and go and watch some TV or something then do it some more.

Nearly done. Make sure the oil level in the pump is a few mm higher than the seal position so that when you push the seal in it doesn't trap air. I used retainer because the seal is not a particularly tight fit although its effectiveness is questionable since everything is covered in oil.

Remove the syringe that was sucking on the temperature compensator diaphragm and the pipe (hot air gun softens Araldite quickly). Measure the position of the compensator diaphragm. If you got the vacuum right then it will be too near the end and there is a risk of ejecting the oil seal when the pump is hot (been there, done that). Put the pump in the vice and undo two of the three torx screws holding the dome down about 1/2 turn. Slowly (slowly) release the third torx screw a until a small amount of oil leaks from the pump. Tighten everything down and measure the diaphragm position. Repeat until the diaphragm position is where you want it to be (22mm from end is my setting). Final tighten the torx screws. Refit solenoid and screw in drive dog finger tight (it will self tighten in use) and you are done.

I have spent a long time on this, no guarrantee it will work for any length of time or there aren't better methods, its a voyage of discovery. I have the luxury of retirement and another car so project work doesn't bother me athough I do hate taking the inlet manifold on and off, there just doesn't seem to be quite the right anount of space.

Good luck, any questions fire away.