All of my initial tests from before had the relay installed. With the relay installed, I had used the battery negative as ground as well as the X13975 wire as ground and was getting similar results to what I just got a few minutes ago with the jumper wire.

At this point, I would agree that it's an issue with the power side

 

A voltage drop means that there is excessive resistance somewhere between the K96 relay socket terminal 87 and the fuel pump connector power pin.

To locate the resistance and repair it, you need to measure voltage at different points in the downstream power circuit to locate where the voltage drops from 12.6V to 7-8V.

The first logical point to do a voltage drop test on the white/blue wire (pin 9) is in JBE connector X11010. This is normally done by backprobing the connector with small gauge probe. Next you would do the same at the X691 connector (fuel pump connector). Then go from there.

Some people would entirely skip the troubleshooting and just run a new wire between the JBE and fuel pump. However, if you decide to take this route, then first verify that the JBE pin for the white/blue wire in the X11010 connector has 12.6V.

 

Which of these connectors has those wires you mentioned above? I have absolutely zero electrical engineering knowledge so forgive my ignorance. At this point it might just be easier to replace the car lol. (Also, ignore the K96 relay, this is an older photo and I currently still have the jumper wire attached)

 

Sorry, I misdiagnosed the voltage drop detected in your downstream fuel pump circuit as excessive resistance. High resistance would only cause a voltage drop in a loaded circuit not an unloaded circuit. Since your voltage tests were done in an unloaded circuit, the correct diagnosis is a short to ground somewhere in the downstream fuel pump circuit. This new information is unlikely to affect how you would identify the location of the short or how you would repair it.

 

I'm not sure, but for any white/blue JBE wire you find, you can verify it as the fuel pump wire by showing loss of voltage upon removal of fuse F46.

 

I think I'm a little confused. What's the next thing you want me to do?

 

It's completely your choice. (1) Locate the short to ground in the white/blue wire and repair it or (2) replace the entire white/blue wire between the JBE and fuel pump.

 

I think this might be where my journey ends. There's just no reasonable way that I can follow that wire through the entire chassis without removing large sections of my interior. The only potentially valuable piece of information that I can give is that the white/blue wire is also reading 8V at the JBE connector

 

You've been on a very difficult journey, but you've also made great progress. Take the night off, and get good night's sleep to see how you feel tomorrow.

Did you measure 8V at the JBE pin or the connector pin? Don't answer tonight.

And tomorrow, you also can consider swapping the original JBE out for the new one to see whether the 8V reading changes to 12.6V.

 

I measured 8V at the JBE pin.

It doesn't bother me to answer questions, and I do want to get my car running, but tracing that whole wire is beyond my space limitations and toolset

 

If this^ information is correct, then the short to ground is inside the JBE not in the white/blue wire, so there would be no wire tracing. In addition, if you did have to install a new white/blue wire, you don't necessarily have to follow the same path as the original wire.

I think you underestimate yourself sometimes because it blows me away how fast you can get some things done.

 

That's a good point, I didn't think about running it a different direction. What should I check on the JBE to see if anything is wrong?

Really? I'm only a 20 year old college student, so my experience and expertise with cars only goes about as far as installing an intake, intercooler, or changing my oil. This job has put me way over my head, but I'm definitely learning a lot from it, so I'm grateful for that

 

Just curious...Why did you reinstall the jumper wire rather than keep using the relay?

I would first check whether you also measure 8V at the JBE pin of the new JBE. Not sure what kinds of tools are available to you but thermal imagers are commonly used to detect shorts to ground.

 

Exactly! The best way to learn is not to fear the unknown.

 

I just hadn't put the relay back in yet

Interestingly, I couldn't get any voltage off the white/blue power wire with the new JBE. I tried multiple grounding points, and made sure fuse F46 and terminals 87 and 30 were receiving appropriate voltage (which they were), but still nothing

 

It's interesting that the new JBE acts different than the original JBE. Was the key fob inserted and the start button pressed? I think the unlabelled top K96 socket provides DME ground for terminal 30 voltage in the relay. What voltage do you measure between those two relay sockets?

Was the K96 relay installed?

 

Yes, the key fob was in and the start button was pressed. The voltage I got off those two sockets was 13.4V (that's just what the battery was currently at)

Yes

 

Hmmm...I wonder whether the new JBE has the same problem as the original JBE but more severe. Specifically, the short to ground on the original JBE depletes less than half of the source F46 voltage whereas the short to ground on the new JBE depletes all of the F46 source voltage.

If possible, you may want to inspect the new JBE board trace from the JBE white/blue wire pin for heat damage caused by a short to ground.

 

Alright, I'll try this tomorrow morning. Lovely how after all that today we end up right back at the JBE . I have to know - is this officially the worst fueling related problem you've seen with these cars on this forum?

 

I can definitely see how you as a car owner trying to fix a difficult fueling issue might view this as the worst.

From my perspective, your fueling issue is interesting because I have never previously come across a LPFP issue caused by a short to ground between the K96 relay and connector X11010 on the JBE circuit board. If you search the internet for causes of 2nd generation Mini Cooper LPFP issues, what you primarily find are discussions about the bad solder joint for the terminal 30G relay (I01068) on the JBE circuit board.

And the most interesting question, in my opinion, is what could have caused two different JBEs to develop a short to ground between the K96 relay and connector X11010 on the JBE circuit board? Maybe floodhound with his PCB repair expertise can help to solve this mystery.

Another mystery is the inability of a scan tool to communicate with and recognize your car. Given that the OBDII port connects to and communicates directly with the JBE via the D-CAN network, it seems likely that the fuel and OBDII issues are interconnected.

 

Just to verify. Were your voltage measurements done on the white/blue wire (white wire with blue stripe) shown in pictures of the white JBE connector in this NAM post?

 

I'm not seeing anything on this new board that indicates heat damage. It honestly looks like it's in really good shape. Should we consider that the issue may be the connection from the white X11010 JBE connector with the white/blue power wire?

 

Yes, they were

 

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A detailed description (or pictures) of exactly how you did the voltage test on the X11010 connector should answer the question.

However, you can also answer the question by unplugging X11010 from the JBE and then measuring voltage directly at the JBE pin corresponding to the location of the white/blue wire in X11010. If you read 12V, then the short to ground is downstream of the JBE. If you read 8V or 0V, then the short to ground is in the JBE.