Fuel Gauge Issue

[sroth004]

All,

My X is an ‘05 4.8is with approx ‘87K miles. I’ve read many posts about the fuel gauge in the e53, cross-over pump issues and lack of access to the last quarter of the fuel, etc...but could not find this one, thoughts would be appreciated.

Was at about a quarter full and filled up the tank last week. Pump shut off where I would have expected in term of gallons so I know the tank is full. Started the X and fuel gauge went to about 2/3 full. Shut down and restarted, went to the same place. Over the next 30 or so minutes of driving the gauge slowly increased to full.

I did not access the hidden menu and check fuel levels in each side, by the time I got to my destination, the gauge was registering correctly. If my research was correct, the passenger side is about 1/3 of the total fuel so the issue is likely that side’s sensor, or not....

Given the gauge level did rise slowly to where it should have been, your thoughts on whether this is a sensor, wiring, and likelihood of it being the passenger side would be appreciated.

Thanks

Steve


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[EODguy]

Stuck sending unit/float

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[oldskewel]

It sounds like a mechanical problem with the right side float, which is part of the fuel pump assembly there. Easy to access under the rear seats, but I would first get that hidden menu on speed dial and get confirming measurements next time you fill up like that. If you want to do some testing to confirm a mechanical problem vs. electrical, you might try sitting there with the ignition on, engine off and see if the level increases.

Also, it could be that whatever problem this is will give accurate readings pretty much all the time except immediately after filling up as you observed here. Until the problem gets worse ...

[andrewwynn]

You prob had an intemittent bad reading. Use test 21 to reset the buffer. Then use test 6 to see what the level senders are sending.

I had the same problem you describe when my left sender read high Ω.

I've also had every possible fuel supply problem and solved them.

[sroth004]

Thanks all, I will investigate based on your suggestions and report back. Appreciate the feedback. Stay safe everyone.


Steve

[sroth004]

So I’ve run through 4 tanks of fuel since having the “slow return to full” on the gauge issue a couple of weeks ago and the issue has not reoccurred. Any chance this could be a one time issue (wishful thinking, I do know better) or a sign of things to come?


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[80stech]

Yes it could, sometimes the sending unit contacts will get dirty or coated/corroded and loose contact temporarily especially if it has been sitting for a while. I think ethanol might contribute to that happening as well. I think some people have had luck with using an additive in the gas to help clean the sending unit wiper/contact.

[Lowblock]

Mine does this all the time, I fill up about every 3 weeks and I will say maybe one in 4 fill ups it does this, i have added a "cleaner" and it didn't seem to do anything. Like you I always keep track "kind of" of how much fuel it should take and am fine with that. I will say that it started happening after I pulled it out of service to rebuild the trans and front end for about a year. The first fill up it did this but then subsided for a few. I have also noticed that it does not matter how much fuel is in the tank when you go to fill it up and it also fluctuates how long before it reads full again. Sometimes its on full by the time I get home, sometimes it takes a couple trips to work (approx. 10 miles) before it reads full. Also here in my state our fuel is pumped for you, and sometimes the attendants don't get the nozzle in correctly and it pops off before its actually full, most places around here will not "top off" so telling them its not full doesn't do anything. It has not really bothered me so I have not done anything more then trying the additive. Mine is an 03 4.4 however I also have a 03 4.6 and it has never done it, both have similar miles but the 4.6 lived a much much harder life then the 4.4 until I got it. To me it would be more concerning that the bottom part of the gauge is not working correctly, thats why ive only gone as far as I have.

Dave

[andrewwynn]

I wrote a how to clean/refurbish the wiper for the float. BMW has a TIS about too little spring pressure and you can add more. Search AWR-Fix title. If not listed seaxh thread started by andrewwynn.

[sroth004]

Thanks all and Andrew for the reference to your article. I will update if anything changes or if/when fixed.

Steve


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