N51 fuel tank,fuel pressure loss

image Today this car kicked my ass,,,,finally figured out the problem,,,,2011 E90 N51 engine,,,,,check engine light on,,,the fault was lean mixture bank 2,,,, so I checked adaption values,,,,found bank 1 at 8% and bank 2 at 9%,,,,so I smoke tested the intake system no leaks,,,smoke tested the exhaust system no leaks,,,,I smoke tested the valve cover no leaks,,,,I then checked the oil cap and found to much vacuum inside the engine,,,,so I replaced the valve cover,,,I reset the adaption values and test drove the vehicle,,,,the fault came back with the same problem,,,,,so the next day I started all over,,,,but I noticed when I started the car up the next morning,,,,the idle surged slightly,,,,almost like it was a misfire,,,,so I tossed in some ignition coils,,,,that did not fix the problem,,,,so I re smoked the intake and valve cover again to make sure I didn’t miss anything,,,,so I went back to basic,,,,air,fuel,and spark,,,,I never checked fuel,,,,I checked the fuel pressure,,,,ok I have a problem 3.5 bar pressure,,,,it should be 5.0 bar,,,,,I remove the fuel tank cover to expose the fuel pump.image So I looked inside the fuel tank,,,,,look what I found,,,,my problem that kicked my ass,,,,look at the short rubber hose inside the tank,,,,notice a small cut in the hose,,,,that’s my fuel pressure loss,,,,the only fix is to replace the fuel tank,,,,the hose is built in to the fuel tank.image Here the new fuel tank,,,,it looks like they changed the hose to a differs type of rubber hose so it won’t crack again.

This entry was posted in Uncategorized and tagged , , , . Bookmark the permalink.

8 Responses to N51 fuel tank,fuel pressure loss

  1. a.a. says:

    Looking back, is there anything you could have done differently to lead you in the direction of the problem sooner?


    • Hahaha good question,,,,,I wish I would have checked fuel pressure sooner,,,,but as a BMW tech,,,,we have seen the valve cover go bad more often then the gas tanks,,,,,I guess I just went for what is the most common problem ,,,,,instead of checking all 3 things first,,,,fuel,spark and air.




  3. Christopher says:

    I have the same problem now.How hard do you think it will be to replace that hose?I want to try that instead of replacing the whole tank.


    • I don’t know if you can just replace that hose,,,,the hose camps will have to cut off carefully and you don’t want to break the plastic fittings,,,,and while cutting no sparks please because of the gasoline,,,,this doesn’t sound like a good idea.


      • James says:

        Is the standard N52 (not SULEV) immune from this problem? I have avoided CARB compliant models as a rule due to the extra complexity and cost down the road. I know the M56 can be much more costly to repair for even minor problems such as a fuel pump when compared to the M54 due to California’s emissions requirements.


      • Yes I believe it is immune


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s