[SnapCoupe]

Hi guys,

Since I have owned my car I have been chasing down the cause of the long crank cold starts that I get every time the car sits for more than a few hours. For the longest time I thought it was due to my HPFP, but once I replaced that, the long cranks were still occurring. Over the past few months since replacing my HPFP I feel as if they have been happening more frequently, so I decided to log a few of them to see whats going on.

Here are 3 long crank cold starts:

https://datazap.me/u/geirsenk/long-c...og=1&data=3-13

https://datazap.me/u/geirsenk/long-c...og=2&data=3-13

https://datazap.me/u/geirsenk/long-c...og=0&data=3-13

And for a baseline, heres a log of when the car fired up pretty normally (still cold).

https://datazap.me/u/geirsenk/more-c...=2&data=0-3-13

The biggest contributing factor from what I can see has to be the rail pressure before cranking over. In all of the logs it is at 18 PSI, which I know for a fact is low. Considering I have a new motor with new injectors, new HPFP, and the starter/battery are fully healthy, I have narrowed it down to the fueling before the motor. This leaves me with either the LPFP or the fuel regulator. Either the LPFP isn't priming as much as it should, or the lines are losing a lot of pressure while sitting. My LPFP sounds fine when it primes and doesn't give me any codes or drivability issues either. Anyone have any ideas as to what to look for or test? I really want to avoid blindly replacing any parts at this point.

Cheers.

[F80_M3llow]

Was the car recently programmed? As you stated you can hear the lpfp priming but that doesn't necessarily mean it's pushing enough fuel to the front. Also have a look at the ekps control unit. This Module controls the lpfp. Also how many miles on the vehicle and mods?

[lucasmiller2015]

When I had long cranks, the dealer replaced both the hpfp and the high pressure sensor (part number 13537620946). Maybe try replacing that as well?

https://www.fcpeuro.com/products/bmw...re-13537620946
https://www.getbmwparts.com/oem-part...re-13537620946

[Pladi]

There is a procedure in ISTA to keep running ur low pressure fuel pump for longer times.

I would do that and check ur rail pressure with car off. See how it changes. Whether it builds up then drops etc.. Then u know something is ot holding pressure. If it does not change much ur fuel pressure sensor could be bad like the above post mentioned.

It could be good for high pressures but not sensitive enough for low pressures..

[SnapCoupe]

Originally Posted by F80_M3llow

Was the car recently programmed? As you stated you can hear the lpfp priming but that doesn't necessarily mean it's pushing enough fuel to the front. Also have a look at the ekps control unit. This Module controls the lpfp. Also how many miles on the vehicle and mods?

No, car was not recently programmed. Car has around 95k miles, new motor has around 10-15k I think. I'll look into the EKPS.

Originally Posted by lucasmiller2015

When I had long cranks, the dealer replaced both the hpfp and the high pressure sensor (part number 13537620946). Maybe try replacing that as well?

https://www.fcpeuro.com/products/bmw...re-13537620946
https://www.getbmwparts.com/oem-part...re-13537620946

I might look into this once I narrow down some other ideas first. I find it hard to believe that it is the high pressure sensor as the rail pressure is fine as soon as the car starts to turn over. I don't think the high pressure sensor would change anything in regards to priming the rail.

Originally Posted by Pladi

There is a procedure in ISTA to keep running ur low pressure fuel pump for longer times.

I would do that and check ur rail pressure with car off. See how it changes. Whether it builds up then drops etc.. Then u know something is ot holding pressure. If it does not change much ur fuel pressure sensor could be bad like the above post mentioned.

It could be good for high pressures but not sensitive enough for low pressures..

I'll check into that. I browsed ISTA the other day in search of a test like this and couldn't find one. I figured there has to be an easier way to test the low pressure system other than tapping a line with a traditional gauge. Why BMW didn't put a low pressure sensor in these cars really doesn't make sense.

[juld0zer]

That function is part of a test module. If you wanted to run the low pressure pump constantly you could just provide direct fused power to the pump under the seat.

The proper way to test the low pressure system is to also check the plausibility of the sensor reading vs a known good gauge that is teed into the feed line.

Based on those logs I'd say your pressure sensor is good because the data supports the symptoms you are experiencing. You should at least have 4-5bar in the rail, indicating the low pressure side is at least providing enough pressure.

[SnapCoupe]

Originally Posted by juld0zer

That function is part of a test module. If you wanted to run the low pressure pump constantly you could just provide direct fused power to the pump under the seat.

The proper way to test the low pressure system is to also check the plausibility of the sensor reading vs a known good gauge that is teed into the feed line.

Based on those logs I'd say your pressure sensor is good because the data supports the symptoms you are experiencing. You should at least have 4-5bar in the rail, indicating the low pressure side is at least providing enough pressure.

This is kinda where i'm leaning now. At this point I am trying to figure out if my LPFP is just a bit tired and isn't pumping as much fuel as it used to during the priming phase, or, theres some sort of leak in the system allowing pressure to escape as the car sits. The latter could be plausible as I am cat-less and get a little bit of fuel smell when driving anyways, but I have yet to see an obvious leak.

[The Silver Slammer]

If you smell fuel while driving, I would check all of your fuel line connection points post hpfp. Probably a leak somewhere allowing air in the lines somewhere or even a leaky injector making it hard to build pressure upon startup.

[Chris_Rav]

I had long cranks for a while. Continuously got worse until the starter finally died on me. Could be your starter beginning to go. Might be your best case scenario as I had the car die and I was able to diagnose, source parts, and repair it all within a day with basic tools for less than $300.

[SnapCoupe]

Originally Posted by The Silver Slammer

If you smell fuel while driving, I would check all of your fuel line connection points post hpfp. Probably a leak somewhere allowing air in the lines somewhere or even a leaky injector making it hard to build pressure upon startup.

The fuel smell is purely from the catless DP. I only smell it outside of the car. Injectors are fine.

Originally Posted by Chris_Rav

I had long cranks for a while. Continuously got worse until the starter finally died on me. Could be your starter beginning to go. Might be your best case scenario as I had the car die and I was able to diagnose, source parts, and repair it all within a day with basic tools for less than $300.

Starter isn't the issue. I'm only getting 18PSI in the fuel rail prior to cranking. Normal fuel pressure in the rail is typically 60-80PSI.

[GoRomeo]

https://www.e90post.com/forums/showthread.php?t=775703

[juld0zer]

Originally Posted by SnapCoupe

The fuel smell is purely from the catless DP. I only smell it outside of the car. Injectors are fine.



Starter isn't the issue. I'm only getting 18PSI in the fuel rail prior to cranking. Normal fuel pressure in the rail is typically 60-80PSI.

For a conventional EFI rail, eg N52 or if the HPFP has failed.

Stuck open injector would usually cause a rich miss, sooty/smoky exhaust and glowing cat if present. Have you been able to measure a voltage at the low pressure pump when it primes?

[SnapCoupe]

Originally Posted by juld0zer

For a conventional EFI rail, eg N52 or if the HPFP has failed.

Stuck open injector would usually cause a rich miss, sooty/smoky exhaust and glowing cat if present. Have you been able to measure a voltage at the low pressure pump when it primes?

This is going to be the next course of action when I get the chance. The LPFP sounds healthy when priming, but I plan on double checking the voltage to be sure.

[Welcome to NBA Jam]

I hope you figure this out cause I'm pretty close to replacing my fuel pressure regulator for shits to see if it fixes the problem. It only seems to happen when it's near freezing, which makes me wonder if something is not quite sealing as well as it used to anymore.

[SnapCoupe]

Originally Posted by Welcome to NBA Jam

I hope you figure this out cause I'm pretty close to replacing my fuel pressure regulator for shits to see if it fixes the problem. It only seems to happen when it's near freezing, which makes me wonder if something is not quite sealing as well as it used to anymore.

This is probably going to be what I do next if the LPFP checks out fine(which I think it will). I have a strong feeling that the regulator is just reading an incorrect value and isn't priming the system accordingly.

[DiFFv1]

Originally Posted by SnapCoupe

This is probably going to be what I do next if the LPFP checks out fine(which I think it will). I have a strong feeling that the regulator is just reading an incorrect value and isn't priming the system accordingly.

Let me know if that helps, Cold starts are a pain sometimes

[SnapCoupe]

Bumping for an update.

I finally got around to doing a full test of the fuel system. I Tee'd a fuel pressure gauge into the HPFP line and tracked the pressure compared to what the DME was commanding the LPFP to do through INPA. The pressure differences confirmed that my LPFP is working just fine, leaving the culprit to be the "fuel pressure regulator" or "fuel sending unit" (I have heard it called both) on the driver side of the fuel tank. From the research I have done, on 2011 N55 cars without the low pressure fuel sensor, this tends to be the fix if the HPFP has already been replaced and no other codes are present. From my understanding, the fuel pressure regulator monitors and sends fuel from the left side of the tank to the LPFP on the right side of the tank.

https://www.fcpeuro.com/products/bmw...ft-16117163295

The part isn't too bad cost-wise, and the DIY is pretty simple. It should pretty much involve taking the rear seat out and pulling the unit out along with the fuel lines that run to the LPFP. I am currently waiting on the part to arrive and will check back once I install it.

[Welcome to NBA Jam]

Looking forward to the update! I'll tackle that this summer if it works for you.

[Chris_Rav]

Originally Posted by SnapCoupe

Bumping for an update.

I finally got around to doing a full test of the fuel system. I Tee'd a fuel pressure gauge into the HPFP line and tracked the pressure compared to what the DME was commanding the LPFP to do through INPA. The pressure differences confirmed that my LPFP is working just fine, leaving the culprit to be the "fuel pressure regulator" or "fuel sending unit" (I have heard it called both) on the driver side of the fuel tank. From the research I have done, on 2011 N55 cars without the low pressure fuel sensor, this tends to be the fix if the HPFP has already been replaced and no other codes are present. From my understanding, the fuel pressure regulator monitors and sends fuel from the left side of the tank to the LPFP on the right side of the tank.

https://www.fcpeuro.com/products/bmw...ft-16117163295

The part isn't too bad cost-wise, and the DIY is pretty simple. It should pretty much involve taking the rear seat out and pulling the unit out along with the fuel lines that run to the LPFP. I am currently waiting on the part to arrive and will check back once I install it.

Do you have any other symptoms other than the long cranks? Any random check engine lights when accelerating or while under WOT ? I have been trying to track down a misfire issue happening around 6k rpms WOT. Coils, plugs, and now hpfp have been replaced and the problem still persists. I was getting the 2BDE and 2BF0 shadow codes and longer than usual cranks so replacing the hpfp eliminated those (so far the codes havent come back but its only been a day).

[DiFFv1]

Originally Posted by Chris_Rav

Do you have any other symptoms other than the long cranks? Any random check engine lights when accelerating or while under WOT ? I have been trying to track down a misfire issue happening around 6k rpms WOT. Coils, plugs, and now hpfp have been replaced and the problem still persists. I was getting the 2BDE and 2BF0 shadow codes and longer than usual cranks so replacing the hpfp eliminated those (so far the codes havent come back but its only been a day).

Regulator , Take a look at my recent Posts..

[SnapCoupe]

Originally Posted by Chris_Rav

Do you have any other symptoms other than the long cranks? Any random check engine lights when accelerating or while under WOT ? I have been trying to track down a misfire issue happening around 6k rpms WOT. Coils, plugs, and now hpfp have been replaced and the problem still persists. I was getting the 2BDE and 2BF0 shadow codes and longer than usual cranks so replacing the hpfp eliminated those (so far the codes havent come back but its only been a day).

No CEL lights or misfires that will throw codes. Sometimes under certain situations where the motor is under high load there will be a hesitation initially that feels like a light mis, but not enough to throw a code.

Originally Posted by DiFFv1

Regulator , Take a look at my recent Posts..

I have been super busy as of recently with starting a new job, moving, and graduating college, so I haven't had any opportunity to do the regulator job yet. I read your other thread and saw that you decided to tackle it. I look forward to hearing your update if you end up doing it before me.

[HeyTeeee]

Originally Posted by SnapCoupe

No CEL lights or misfires that will throw codes. Sometimes under certain situations where the motor is under high load there will be a hesitation initially that feels like a light mis, but not enough to throw a code.



I have been super busy as of recently with starting a new job, moving, and graduating college, so I haven't had any opportunity to do the regulator job yet. I read your other thread and saw that you decided to tackle it. I look forward to hearing your update if you end up doing it before me.

Thought I'd give you a little update from my experience. I did the regulator (day before I did my VC). Good news, pressure stayed at 74.3 an hour after shutting the car off so it held pressure. Before I observed it drop from 74.5 down the 18 psi over an hour. I think I mentioned that in another fueling post. Bad news, I broke a piece of my guide rail doing the VC so while I did observe rail pressure dipping below 700 I haven't been able to do any complete logs bc I'm afraid about my timing chain doing some ghostrider shit lol!