[SnapCoupe]

Since purchasing my car last September with 70k miles (now has 86k) I have been fighting a long crank/cold start issue with little to no progress. The long crank occurs whenever the car has been sitting 4 hours or more and the temperatures are 60 degrees F or lower. Every morning when I go to leave for work, i'll start the car and it will continue to crank until I press the button again to turn it off, and once more to restart it. Upon the second attempt it will fire up immediately. Last month I had a factory fresh N55 installed by BMW and the problem is still there, so that rules out injectors, vacuum, and a few other things.

I have run multiple fuel pressure tests and my HPFP passed with flying colors and holds pressure just fine under load. This leads me to believe that it might be the low pressure pump that might be the issue, but considering the pump primes as it should every time I unlock the car I am unsure how it would contribute to the long crank.

This morning I logged a long crank in hope of getting to the bottom of this. I started logging before starting the car for the first time and it continued to crank as always. When I pressed the button again to stop it/restart it, MHD decided to stop logging. What you're seeing in the log is what the car is doing during first crank.

httphttps://datazap.me/u/geirsenk/co...og=0&data=3-11

Thanks in advanced for any help!

[weehe126]

Took over a year for my hpfp to throw a code while I had long cranks. All pressure tests were fine as well. Replaced the HPFP and no more long cranks.

[SnapCoupe]

Originally Posted by weehe126

Took over a year for my hpfp to throw a code while I had long cranks. All pressure tests were fine as well. Replaced the HPFP and no more long cranks.

I do have the shadow codes on MHD for the HPFP, but as I mentioned before, I have used BMW's ISTA program to run multiple fuel system tests with everything coming back as nominal.

I just showed the log to an experienced tech at my dealership and he mentioned that the LPFP could be slowly dying and not providing enough pressure to fully prime the system all the way up to the HPFP. I'm going to get a fuel pressure gauge on the car right before the HPFP and try to get some readings in the next couple of days. If that's not the case i'll just bite the bullet and replace the HPFP.

[weehe126]

Originally Posted by SnapCoupe

I do have the shadow codes on MHD for the HPFP, but as I mentioned before, I have used BMW's ISTA program to run multiple fuel system tests with everything coming back as nominal.

I just showed the log to an experienced tech at my dealership and he mentioned that the LPFP could be slowly dying and not providing enough pressure to fully prime the system all the way up to the HPFP. I'm going to get a fuel pressure gauge on the car right before the HPFP and try to get some readings in the next couple of days. If that's not the case i'll just bite the bullet and replace the HPFP.

Even when I got the codes everything was fine in ISTA. I wasn't even running out of fuel on E40 maxing the stock turbo. It's something with an internal seal leaking pressure that causes the long crank. Highly doubt you have a LPFP issues before a HPFP issue.

[lwgrenier]

SnapCoupe I was having semi-long cranks since I bought my car in September 2017 with 54k miles. Once it fired up the car would run fine until very recently. I took some logs at idle and WOT to compare rail pressure. The pressure at WOT was fine at ~2200psi. However at idle my pressure was ~80psi which is very low. I replaced my HPFP on Wednesday and the car has been starting, idling, and running much better. No more long crank and plenty of pressure at idle. Hope this helps.

[Johnny Boost]

It could be your starter. My car had the same symptoms and one day the starter died without throwing prior codes.

[vespa]

Fuel pressure should be over 70psi but your log is showing 37psi. Looks like a LPFP issue to me.

[SnapCoupe]

Originally Posted by Johnny Boost

It could be your starter. My car had the same symptoms and one day the starter died without throwing prior codes.

The new motor came with a brand new starter. That shouldn't be the issue.

Originally Posted by vespa

Fuel pressure should be over 70psi but your log is showing 37psi. Looks like a LPFP issue to me.

I agree. I think i'm going to replace the pump soon to see if it improves.