[wrevilo]

My N55 335i is currently in the garage having a bunch of work done following recent replacement of the HPFP, LPFP and LPFP filter/regulator. This is comprising:

• a replacement HP fuel sensor to solve codes 2BF8 and 2C01 that popped up on the journey home after the works above on 03 February 2024
• a replacement pre-cat lambda sensor to solve codes 2CF4 and 2D2F that was found subsequent to the code above on 06 March 2024
• replacement of 2x pre-turbo gaskets and the post-turbo pipe to resolve air leaks identified through a smoke test at the time of the works above
• a replacement diverter valve
• a replacement wastegate actuator
• fitting of a stainless-steel exhaust

Added to the above is desired resolution of an apparent fuel leak, which first manifested itself as a strong smell of fuel outside the car after a 35-minute drive on my commute. I first thought that this might have been the car simply running very rich due to the issues relating to the HP fuel sensor and the lambda sensor.

However, after a subsequent shorter journey, the car stank of fuel outside the car, but also left what I assumed was a line of fuel on the ground after having been sat for a couple of minutes nose up on a ramp up to another level of the local tip.

Apart from having driven the car home I have not driven the car since. The car was taken away on a trailer to the garage who have been unable to find a leak or evidence of a leak. They have smoke tested the evap system and inspected the car thoroughly including getting it up to temperature and driving it.

My first thought was that the leak would be as a result of the works to the fuel system. However, this does not appear to be the case. Does anyone have other ideas of what to look for and how?

[marvinstockman]

Arrange with the shop for you to drive the car for 30 minutes or so, and then drive straight to the shop and have them put car directly on the lift. You stay and watch.

[wrevilo]

Thanks, I will definitely do that when I collect the car.

[jbash87]

Does anyone have other ideas of what to look for and how?

Pop the rear seat out and check for fuel around the gas tank caps. If those weren't screwed on all the way after replacing the in-tank fuel pump it could be leaking from there. Don't ask me how I know...

[wrevilo]

Thank you, that sounds terrible!

I think checking under the rear seats has been done already. Certainly, there was no smell of fuel in the car when outside it stank. Did you have any smell of fuel in the car?

I am aware of how difficult it is to replace the the in-tank units, as I was present at the time!

[jbash87]

Didn't necessarily smell it in the car because there are caps which seal the cabin. But...
It was early in the morning and I needed fuel before work. Pump didn't shut off as the fuel was spilling out in-tank caps and onto the ground. Everything smelled.
Now that I'm thinking about it, it's probably worth noting that I did have my dash tell me the gas cap was loose during this fiasco. If you're not seeing that error then your tank is probably sealed.

[wrevilo]

Thanks. I have not had any lights or error codes relating directly to the fuel system, nor do I have the car yet.

I might get the car this weekend and will be undertaking a decent test drive before taking it away from the workshop. The mechanic has offered to come along and log at the same time, which might be useful.

[wrevilo]

I wanted to update this after me and my mechanic discovered the fuel leak over the weekend, which was the first opportunity I have had to drive the car since posting. We filled up with Shell V Power and drove the car reasonably hard before returning to the unit, at which point there was a line of fuel on the floor.

We discovered that a line on the LPFP, which was installed by the same mechanic, was not connected. This could have been incorrectly installed or become disconnected through regular use. If the latter, it will be concerning because this could occur at any point when I start using the car again. We also have Valvetronic matters to resolve (new actuator necessary) and a squeak from the vibration damper to sort before this.