[kevlarblue]

Cold starts are fine - fires right up and runs smooth. But if I start the car within 30-40 minutes after shutting down (still warm) it cranks for a long time and stumbles a bit when it does fire up. It will smooth out pretty quick but it's been driving me crazy.

I also have the shadow code 2FDB Fuel High Pressure nach freigabe der Einspritzung which apparently means pressure not building at start - almost exactly what I am experiencing but only during warm starts.

Through all my research and reading the forums my 2 leading theories are HPFP or leaking injectors. Since both are fairly expensive I don't want to throw either part at it without another opinion. So far I have done:

Coils and plugs last weekend
Walnut blasting ~3K miles ago
Crank position sensor 500 miles ago
The test with injectors out of the motor and cranking (none of them leaked)

The tips of my index 12 injectors were pretty black when I pulled them out (normal?) and I do smell fuel around the car occasionally. But I couldn't get any of them to show me a leak and none of the plugs smell like fuel when I pull them out.

Other than the hard start the car runs great - no fuel starvation symptoms and no active DME codes. I am FBO with stock turbos and JB4 at 112K miles. I'm either going to spend the money and get a new HPFP (out of extended warranty coverage) or swap my injectors for used index 12s.

I'm hoping to poll the crowd: which of the 2 expensive options will fix my hard starts? Thanks for reading - I appreciate any input.

[swellengear]

Sounds like you might have a small leak on an injector, although the code points towards a hpfp issue. Are you able to post a log?

If this only happens when warm, try pulling the plugs after 45mins and see if any of them are wet/damp with fuel. Leak may be small enough that the plug(s) dry out while it cools - so no cold start issue.

[kevlarblue]

Originally Posted by swellengear

Sounds like you might have a small leak on an injector, although the code points towards a hpfp issue. Are you able to post a log?

If this only happens when warm, try pulling the plugs after 45mins and see if any of them are wet/damp with fuel. Leak may be small enough that the plug(s) dry out while it cools - so no cold start issue.

I did the try the plugs while it was warm and it was inconclusive - I had just done the injector test and there was fuel everywhere.

I can definitely post a log from the JB4, would a warm start with issue be the most helpful? Or just a pull?

[kevlarblue]

Originally Posted by swellengear

Sounds like you might have a small leak on an injector, although the code points towards a hpfp issue. Are you able to post a log?

If this only happens when warm, try pulling the plugs after 45mins and see if any of them are wet/damp with fuel. Leak may be small enough that the plug(s) dry out while it cools - so no cold start issue.

Here is a 3rd gear pull from my JB4. I'm working on getting MHD installed in case this doesn't make sense to anybody else.

[ATTACH]undefined[/ATTACH]

[marcell1401]

Any news on this? I have exactly the same issue. Injectors dont leak. Stumble on hot start. Plugs and coils are new and gapped correctly. Maybe an air leak or bad o2? I habe read that cold start runs from ecu values and hot start ist based on map/maf and o2 afr.

[swellengear]

Originally Posted by kevlarblue

Here is a 3rd gear pull from my JB4. I'm working on getting MHD installed in case this doesn't make sense to anybody else.

[ATTACH]undefined[/ATTACH]

No attachment. Can you post a datazap link?

[kevlarblue]

Originally Posted by swellengear

No attachment. Can you post a datazap link?

https://drive.google.com/file/d/1Kge...ew?usp=sharing

Sorry, hopefully that works.

[kevlarblue]

Originally Posted by marcell1401

Any news on this? I have exactly the same issue. Injectors dont leak. Stumble on hot start. Plugs and coils are new and gapped correctly. Maybe an air leak or bad o2? I habe read that cold start runs from ecu values and hot start ist based on map/maf and o2 afr.

Update from this weekend: I found a rebuilt HPFP and swapped it out with no change to the symptoms. If anything it made the problem worse - I had a very long cold start crank and smelled a ton of fuel through the exhaust. I cleared the 2FCA shadow code and it keeps coming back.

So now I am working on finding a set of used -12 injectors to put in. Once they arrive and I get them put in I'll post a status update if it worked.

[marcell1401]

Waiting for the update.

Did you leak test them?

[kevlarblue]

Originally Posted by marcell1401

Waiting for the update.

Did you leak test them?

As shown in the picture from my first post, yes. I hooked them up to the fuel rail outside the engine, unplugged their electrical connectors and cranked the engine. Not a drop came out of any of them. I'm curious to try again with the new HPFP but I don't have the time or motivation right now.

[marcell1401]

I dont think that the hpfp would make a difference when a injector is leaking.

I have the same issue as you do.

Ill check for valve cover leaks, boost leaks, and clean maf and map sensor.

Ill let you know if o can figure something out

[kevlarblue]

Originally Posted by marcell1401

I dont think that the hpfp would make a difference when a injector is leaking.

I have the same issue as you do.

Ill check for valve cover leaks, boost leaks, and clean maf and map sensor.

Ill let you know if o can figure something out

I appreciate the help! From what I understand the pressure from the fuel rail leaks by an injector that doesn't close all the way. In my mind, the greater the pressure behind the injector the greater the leak. And if my old HPFP wasn't building full pressure, and the new one probably is, the leak could be worse now. But I'll admit that my understanding about this engine is still being developed after 6 years of ownership.

What year/mileage is your car? Do you have -12 injectors?

[marcell1401]

Mine is a 2007. yes i do have full set od index 12. a bad hpfp would also cause rough starts when cold, not just when warm.

Does your car crank longer than usual, or do you have a short crank, after which the engine fires up but stumbles for like 1 or 2 engine rotations before it smoothes out?

[kevlarblue]

Originally Posted by marcell1401

Mine is a 2007. yes i do have full set od index 12. a bad hpfp would also cause rough starts when cold, not just when warm.

Does your car crank longer than usual, or do you have a short crank, after which the engine fires up but stumbles for like 1 or 2 engine rotations before it smoothes out?

Before the HPFP it would only hard start when warm, but today was a very hard start after sitting for 48 hours and I smelled more fuel than I have ever before. If it's a hard start it will stumble for 1-2 seconds but if it fires right up (short crank like I expect) then it runs smooth the whole time.

[marcell1401]

Can u please do a log next time you start her up? I think it would help if we can see the fuel pressure and timing on start up. Ill also do a log tomorrow

[swellengear]

Now that it's starting to struggle when cold starting, try the plug test again after its been sitting overnight. (after a drive) Certainly sounds like a leaky injector(s). Regarding your log, I have 'requested access'. You can also upload your log to https://datazap.me/ and share the link with us.

[swellengear]

Had a look at your log, your hpfp looks fine. So likely culprit is a leaky injector.

https://datazap.me/u/uwe-merkle/log-...data=1-5-10-17

[kevlarblue]

Originally Posted by swellengear

Had a look at your log, your hpfp looks fine. So likely culprit is a leaky injector.

https://datazap.me/u/uwe-merkle/log-...data=1-5-10-17

Thank you for that! I really appreciate the info. Is there any kind of log that could pinpoint which cylinder(s) might have the leaking injector? I'll try pulling the plugs again but another source of data would be awesome.

[swellengear]

Your AFRs for both banks look good, and are matching. So that doesn't tell us much. There are some timing corrections on cylinder 1, which MIGHT point towards a leaky injector. I would drive the car for a little bit(no need to drive it hard), park it up, and pull the plugs after the car has been sitting for a good few hours. Give them a smell as well, and also inspect them visually.

Here is a great guide for interpreting your data logs:
https://bmwtuning.co/bmw-n54-data-logging-with-jb4/