mr_hyde

Hello all! My 2011 CS started having issues a few months ago. If the car sat for a couple of days, it would take a few extra cranks to start. It would eventually start and would run fine. Hot/warm starts during the day (i.e. running errands or even parking at work for 8 hours) were perfectly fine - it started instantly. The symptom started getting worse. Now, that 8 hour park at work can take longer to start. The car has 148k on the clock and my best guess from reading the service history is the in-tank fuel pump was original which probably meant the fuel filter was original so I replaced those. There was no change or improvement.

The next thing google threads (including some here on Rennlist) show is to change the high pressure fuel pump. Since this isn't as inexpensive as the in-tank unit or as easy to get to, and because some people with these symptoms have replaced their HPFP and not solved the problem, I wanted to double check a couple of things...

Is there a fuel pressure regulator or a check valve in the system that I should replace first? The car starts perfectly when it hasn't been sitting (although this is degrading also) which suggests to me that the pressure or fuel volume in the fuel line is slowly draining away over time. 2 or 3 hours and the car starts right up. 2 or 3 days and the system is mostly dry. Thoughts? Any other ideas? The plugs and coils are both relatively new. The injectors are probably original and in a perfect world, I'd pull them and have them cleaned in a lab and balanced or replaced. Could this issue be caused by anything past the HPFP?

Does anyone have additional details on people with these codes replacing the HPFP and it not solving the issue? What did it end up being? Any suggestions much appreciated!

mr_hyde

If the HPFP is leaking off pressure, is the fuel running back into the tank or passing into the engine?

AnAlbumCover

BMW N55's had a similar "long crank" issue. Most of the time it was the HPFP. Sometimes it was leaky injectors. Neither are particularly easy to replace but with the HPFP, its just 1 part vs 8?

This is a long shot but maybe try an injector cleaner (Redline etc.)

mr_hyde

Good point on the injector. I would expect if an injector was sticking open it would be failing while operating too and throw an engine code. My leaking into the engine question was more to learn the design of the mechanism. The camshaft turns the HPFP so will fuel drop back through the pump shaft that is turned and end up in the top of the engine? Unless there is a check valve somewhere that I'm not understanding, it looks like the HPFP is the next thing.

AnAlbumCover

I don't know the answer to your question but on the N55's, they wouldn't stick open but would bleed pressure when the engine turned off. The failure you've describes also happened on the N55's where a check valve in the HPFP and LPFP would leak pressure...pretty much the whole fuel system leaked!

As far as fuel going to the top of the engine?...I don't think I follow. If the system remains "sealed" the fuel between the LPFP, HPFP and injector will remain under pressure (high side and low side) unless there's a leak (injector, HPFP, LPFP). I don't know if we (or any car for that matter) have any check valves that reside outside of the pumps.

mr_hyde

In terms of leaking, I supposed I'm thinking in terms of how coolant can leak out the shaft of a water pump that is starting to fail. I doubt it would be enough fuel to cause an issue anyway. I think I have resolved to replace the pump. Now I just need to decide which pump to buy!

Ripking

My 2011 turbo exhibited similar issues and if I recall the same 1023 code.

it was the HPFP. Cheapest I found was from Porsche of Olmsted in Ohio (onlinePorscheparts). They didn’t charge sales tax for me either which was a big savings on this expensive part.

mr_hyde

To close the loop on this, I replaced the HPFP and it solved the issue. After clearing the codes, the car runs smooth and more importantly, starts quickly with no issues after sitting for multiple days. Some of the DIY threads do a good job with the details of the how-to. I have large hands so I didn't enjoy the job but it was doable. Have a blanket so you can lay across the top of the motor and plan to do most of your work by feel. A 10mm ratcheting box wrench is your best tool...