[Velocity26]

It's really difficult to measure your HPFP performance when you are not logging the target pressure. The thing that looks strange to me is that you are returning to ~725psi while the engine is still in significant boost, but I cannot see if there was a throttle cut, or some other event causing it. Maybe the ECU lowered the target pressure? In either case, your fuel trims only spike to about 20 and are generally much lower than that. Mine go to 34 (which I believe is about the max) which should indicate that the the ECU is doing all that it can to make up for the missing pressure. Sometimes my STFT goes to max and it is still not enough and the motor goes lean and starts to shudder .... makes me shudder too.

[Jeff@TopGearSolutions]

Originally Posted by Velocity26

It's really difficult to measure your HPFP performance when you are not logging the target pressure. The thing that looks strange to me is that you are returning to ~725psi while the engine is still in significant boost, but I cannot see if there was a throttle cut, or some other event causing it. Maybe the ECU lowered the target pressure? In either case, your fuel trims only spike to about 20 and are generally much lower than that. Mine go to 34 (which I believe is about the max) which should indicate that the the ECU is doing all that it can to make up for the missing pressure. Sometimes my STFT goes to max and it is still not enough and the motor goes lean and starts to shudder .... makes me shudder too.

Yea 34% is max. So it could and sounds like it needs even more fuel.

34% extra is a lot BTW.

[Velocity26]

Update for anyone interested, I found a set of series 12 injectors at a reasonable price, so I picked them up along with a new HPFP. Had a friend offer to code my injectors, so I decided to put them in first, then do the pump this weekend.

My HPFP is still bad, the pressure droops significantly under boost, and has a hard time building pressure on start-up. However, several of the symptoms that I had attributed to the HPFP or other causes we resolved by the injectors. The famous Cobb surge is solved and the motor idles and runs perfectly smooth at partial throttle. My bank 2 STFT are much lower than before and the engine will not shudder at full throttle. If I hold full throttle, the pressure will continue to drop, but I am able to get a short log without fear of serious damage. I am comfortable anytime there is adjustment room on the STFT.

I submitted the invoice for the injectors to BMW and we will see if they reimburse.

[Nonecure]

I just replaced the HPFP again and the log looks about the same. It does not dip down as low, but I am running a softer tune until I get this sorted out. Can the stock LPFP be part of the issue? 3 HPFP's with the same crazy drop at 3k rpm, it just doesn't sound right.

http://www.datazap.me/u/nonecure/log...3&zoom=430-472

Any ideas?

.

[Velocity26]

The only way to know if your HPFP is under-performing is to log the requested pressure and the actual pressure. The pressure requested fluctuates up and down constantly, so you cannot tell how well it is working without seeing what is requested.
The blue line is boost requested, Pink is pressure supplied and yellow is boost. You can see where the pressure requested is not a straight line or symmetrical curve, it varies constantly. Ideally, the pink line should mirror the blue one (as it does before the boost kicks in, and after the boost is gone). At high boost, you can see how this pump is failing to keep up with demand.

[Nonecure]

I agree the requested pressure would be a great tool, but I don't see how to log it with the MHD app. I see you're running with Cobb, so obviously you have the feature. Maybe Martial can add that to the MHD log selection. I am tempted just to go with a Stg 2 LPFP to get that out of the way.

[blau808]

I've had my HPFP and all six injectors replaced along with my battery because I have the same issue you guys have - rough idle start sometimes in the morning (but not every morning). No long crank. The issue is still there, have you guys solved your problems?

[Nonecure]

No, I have replaced my HPFP twice and installed a Fuel-it Stage 2 LPFP and still have the same problem. Both pressure transducers look ok, so I'm stuck on this one. When I have some extra time I will need to dig deeper.

[blau808]

Originally Posted by Nonecure

No, I have replaced my HPFP twice and installed a Fuel-it Stage 2 LPFP and still have the same problem. Both pressure transducers look ok, so I'm stuck on this one. When I have some extra time I will need to dig deeper.

I talked to BMW cert "master" mechanic and he says that as long as there are no CEL's and the car drives fine otherwise - then the rough start doesn't matter and is most likely the HPFP (mine has been replaced twice)

I told him that's not very reassuring.... so Ill buy you a beer if you figure this one out.

[Velocity26]

I upgraded to a Stg 2 LPFP and it solved nothing. I honestly felt that my HPFP was at the root of all my problems. I had a friend offer me a great deal on a full set of Rev 12 injectors and I figured I would replace them as insurance since BMW would reimburse me and make them free. Replacing the injectors solved a lot of the problems that I had been attributing to other sources. The car still had occasional long cranks (the HPFP really was on the way out) but the car started and ran smooth as silk. The constant surging disappeared and disparity between the bank 1 & 2 fuel trims tightened up.

About a week or two later, I replaced the HPFP and the low pressure sensor. That solved the low pressure oscillations, the constantly changing low fuel pressure and the high boost lean out. The car stopped giving the Fuel Pump fault and the Fuel Pump plausibility errors. The car currently drives like the day it drove off the assembly line, except a lot faster. I am really glad that I changed the injectors.

[Velocity26]

Originally Posted by blau808

I talked to BMW cert "master" mechanic and he says that as long as there are no CEL's and the car drives fine otherwise - then the rough start doesn't matter and is most likely the HPFP (mine has been replaced twice)

I told him that's not very reassuring.... so Ill buy you a beer if you figure this one out.

I have a Cobb, so I can monitor the HPFP pressure before starting the car. The fuel pressure should climb to about 2,500psi immediately after start-up, if not the HPFP is failing. If I did not drive the car for more than a day, the fuel pressure would stay at about 80 PSI until I revved it up and then the pump would build pressure and the rough idle would go away instantly. Basically, the rough idle is caused by having ~70psi of fuel pressure when the ECU is expecting you to have 2,500psi. You start to notice that the car idles perfect when the HPFP works right and idles rough when the pump is not building pressure.

[blau808]

Originally Posted by Velocity26

I have a Cobb, so I can monitor the HPFP pressure before starting the car. The fuel pressure should climb to about 2,500psi immediately after start-up, if not the HPFP is failing. If I did not drive the car for more than a day, the fuel pressure would stay at about 80 PSI until I revved it up and then the pump would build pressure and the rough idle would go away instantly. Basically, the rough idle is caused by having ~70psi of fuel pressure when the ECU is expecting you to have 2,500psi. You start to notice that the car idles perfect when the HPFP works right and idles rough when the pump is not building pressure.

Good to know. Unfortunately I don't know if I can get the dealership to replace it unless a light comes on somewhere. MHD shows no codes either.

[Velocity26]

Once the pump starts to fail, it will get progressively worse until it fails completely. You may have to wait for it to fail completely, but you still have the extended warranty to protect you. Just before I replaced it, mine ran for about 15 seconds without building pressure so I turned it off. I restarted and it again would not build pressure for another 15 seconds. I finally revved the engine some and it built pressure and acted normally again.

[blau808]

Originally Posted by Velocity26

Once the pump starts to fail, it will get progressively worse until it fails completely. You may have to wait for it to fail completely, but you still have the extended warranty to protect you. Just before I replaced it, mine ran for about 15 seconds without building pressure so I turned it off. I restarted and it again would not build pressure for another 15 seconds. I finally revved the engine some and it built pressure and acted normally again.

So someone else is telling me that its the injectors. Obviously you have monitored this and sound pretty confident its the HPFP. Why would someone suspect the injectors though and are you confident that this is not your issue?

[Velocity26]

Guessing will only get you so far, you need to get some data to locate your problem. Rough idle can be cause by bad injectors and it can be caused by a failing HPFP. If your fuel system is getting 75psi, while it is expecting 2,500, there is only so much it can do to compensate for that. If your car runs rough with good fuel pressure, it is the injectors. If the fuel pressure is way too low, you have a bad HPFP. The symptoms can be pretty similar until your pump fails completely. Check the fuel pressure while the car is running rough and find your answer.

[blau808]

Originally Posted by Velocity26

Guessing will only get you so far, you need to get some data to locate your problem. Rough idle can be cause by bad injectors and it can be caused by a failing HPFP. If your fuel system is getting 75psi, while it is expecting 2,500, there is only so much it can do to compensate for that. If your car runs rough with good fuel pressure, it is the injectors. If the fuel pressure is way too low, you have a bad HPFP. The symptoms can be pretty similar until your pump fails completely. Check the fuel pressure while the car is running rough and find your answer.

I agree about the guessing. I will use MHD to monitor and see.