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-   -   Faulty sending unit(s)? (https://xoutpost.com/bmw-sav-forums/x5-e53-forum/110899-faulty-sending-unit-s.html)

dkl 10-10-2019 01:28 PM

Faulty sending unit(s)?
 
Ran the car through an automated carwash :slap::wow:The car had slightly less than 1/4 tank...so proceed to go get the car filled up. Put in 20 gallons and the fuel gauge is now only registering slightly over 1/2 full. The gauge is climbing super slow - took over 4 trips (approx. 40 miles) to get it to the FULL mark.



Is this a sign of a failing sending unit(s)?

andrewwynn 10-10-2019 04:08 PM

Faulty sending unit(s)?
 
Yes it's exactly what happens when the sending unit reports erratic behavior. You can reset the buffered display to get what it actually reads but you need to refurbish the sender if you want to know for real how much gas you have.

Search awr-fix in titles I have a step by step how to repair a sending unit that is misbehaving.

At least you didn't find out about the problem by running out of gas

dkl 10-10-2019 05:10 PM

Quote:

Originally Posted by andrewwynn (Post 1169842)
Yes it's exactly what happens when the sending unit reports erratic behavior. You can reset the buffered display to get what it actually reads but you need to refurbish the sender if you want to know for real how much gas you have.

Search awr-fix in titles I have a step by step how to repair a sending unit that is misbehaving.

At least you didn't find out about the problem by running out of gas


That shouldn't happen (running out of gas), unless the fuel pump fails. I never drive more than 300 miles on a single tank of fuel, unless I'm on a LA to San Francisco run. Thanks for the repair step by step.

andrewwynn 10-10-2019 05:46 PM

Unless your fuel sender is reporting an extra 10-15L of gas.


Sent from my iPhone using Tapatalk Pro

dkl 10-10-2019 07:37 PM

Quote:

Originally Posted by andrewwynn (Post 1169848)
Unless your fuel sender is reporting an extra 10-15L of gas.


Sent from my iPhone using Tapatalk Pro


I've never solely relied on the fuel gauge on my cars. I've always correlate it with the trip meter, which is reset at every fill up. So, unless, the car somehow is a lot more thirsty than usual, I'm not too worry about running out of gas.

But point noted...may have to get it taken care of soon

andrewwynn 10-10-2019 09:44 PM

My range varies from over 500 to barely over 200 miles. Trip odometer is useless to me.

The problems with fuel system are fairly easy to determine using the hidden menu 6.

I wrote the book on how the system works. Also can be found on xo.

dkl 10-10-2019 11:54 PM

Mine is fairly consistent. I get about 240 miles per 18 gallons strictly city driving. I get 280 to 300 miles per 20 gallons with mix (70% city/30% HWY). So, the trip meter isn't entirely useless in my case.

andrewwynn 10-11-2019 12:33 PM

They can definitely because helpful, but until the gauge goes haywire, the X5 will let you drive to zero DTE every time (there's is approximately 3L of fuel remaining when the DTE reads 0). One guy on xo regularly goes 10 miles past zero. So I recommend trust the gauge until you can't then fix it and trust it once again.

I've been stuck with fuel starvation four times (two times with each X5) each time for a different reason. It's just not smart or wise to think you can outsmart failure; cars will fail you just have to have a safety valve (eg roadside assistance) for WHEN it happens.

Example: never letting fuel get below 1/4 tank will only improve your chances of getting stuck because you are forcing yourself artificial constraints on your range and masking possible defects.

The first time I got stranded was specifically because wife always kept tank above 1/4 and the siphon jet had failed but I didn't know because you can only tell by consuming the tank below 1/4.

Everybody with a BMW and split tank owes it to themselves to drive down to single digits DTE at least once a year to confirm the siphon jet is still working.

You can monitor test 6 to make sure it's working or just have a can of gas in the back in case it's not.

Test for the sending unit also use the test six. If the instant value is no where near the averaged value the sending units are sending flaky values.

When my sending unit flaked out, I filled my tank, it showed like 2/3 of a tank but the instant values showed full.

I reset the gauge and it popped right up to full but within a day or do I saw the values read impossible values.

I drove the car down to 1/4 tank so I could calibrate the right tank sending unit (replacement pump read a non normal value I wanted it to read like factory: 1.4L).

Once I got the right sender calibrated and even before I had noticed the left sender would sometimes read higher than possible.

Example: when the tank has about 28L left the right will be 1.4L. It's impossible for the left to have more than 28 unless there is more than 1.4 on the right.

So, for example If the tank shows 1/3 or 1/2 and the left reads 35L but the right shows 1.4, then most likely the right is reading correctly and the left is reporting more than actual.

If the right reads 0 and left is maybe 20, most likely your siphon jet o-ring has failed. Put in gas immediately and keep left above 28L until you fix the o-ring.

cn90 10-11-2019 08:03 PM

You can run a few bottles of fuel injector cleaner such as Techron over 1-2 weeks and see what happens.

dkl 10-12-2019 01:03 PM

Quote:

Originally Posted by cn90 (Post 1169911)
You can run a few bottles of fuel injector cleaner such as Techron over 1-2 weeks and see what happens.


That's not a bad idea...will definitely give it a shot - thanks. Although, I usually use their Fuel System cleaner, not their Fuel Injector cleaner.

Since the X has be delegated to our spare/3rd car duty, it only gets a fill up every month or thereabouts and it's been drinking Costco gas for the past years or two, so that may have something to do with it? I may even treat it to a couple tanks of the good Chevron stuff to see if it helps :thumbup:


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