Fuel Gauge

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Subsonicnat
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Fuel Gauge

Post by Subsonicnat » 03 Apr 2019, 14:35

Hi guys,Been looking for the subject matter on fuel gauge problems on my XASARA PICASSO EXCLUSIVE 2.0 hdi. 2004''
Gauge showed FULL,Went to Coventry and back showed 1 bar missing,Filled it to the brim cannot put any more in,,BUT continues to FALL and has not reset to FULL..WHY?????.
If I disconnect battery will it RESET to where it should be..
Read other forums all seem to point it has a MIND of its own.
Did Read somewhere on here,,BSI RESET.????.
And can I RESET IT with LEXIA,ALL IDEAS entertained,Mut be doing somewhere 46/50 gallon,Really pleased with that side..
thank You.
Colin.uk.

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GiveMeABreak
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Re: Fuel Gauge

Post by GiveMeABreak » 03 Apr 2019, 15:21

First you should not brim it past the third click.

Next, depending on system the fuel gauge can be estimated based on last measured reading and miles travelled until the next time it takes a measurement.

It’s the way some of these work, so I wouldn’t worry about it unless the tank has been filled and it shows half empty or something silly like that.

Overfilling can upset the system, so be warned.

Subsonicnat
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Re: Fuel Gauge

Post by Subsonicnat » 03 Apr 2019, 16:36

so,,,, the moral to the story is dont top it up.?
but is there a way out of it for now.?.
would as some have done leave the battery off over night,or,,, Can I NOT RESET it.???.
Looking back at your reply Marc,,Apparently it does have a mind of its own,I was right.
lol.

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GiveMeABreak
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Re: Fuel Gauge

Post by GiveMeABreak » 03 Apr 2019, 17:01

Just leave it for now - there is no reset. let the tank run down to under half, then when you next fill her up, stop at the first couple of clicks. Then see what she reads.

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myglaren
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Re: Fuel Gauge

Post by myglaren » 03 Apr 2019, 17:22

I have always brimmed my tanks right up the spout.
Never had a problem until this latest time.
Squeezed 70L in (65L tank)
After the usual 100-ish miles the needle was down by almost ¼.
Then it was up to max again for a few days. I wondered if my son had added some diesel but he hadn't.
Seems to be working again now but will have to keep an eye on the trip meter along with the fuel gauge.

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Paul-R
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Re: Fuel Gauge

Post by Paul-R » 03 Apr 2019, 18:01

I have always, and still do, brim right up to the top.

Subsonicnat
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Re: Fuel Gauge

Post by Subsonicnat » 03 Apr 2019, 18:16

wow,,,,,,,
must admit I didn't expect that answer Marc,
When I topped it up,I did Put the mileage back to "o".

So will just have to keep an eye on it for the next 300 miles,???????/.
to see if it starts to work properly as it use to do around half a tank..oh lor.

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GiveMeABreak
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Re: Fuel Gauge

Post by GiveMeABreak » 03 Apr 2019, 18:49

There’s a technical explanation somewhere I’ll have to dig up if I can try and find it.

The X7 of mine had a failure of the electronic gauge on the dash to ever get back to 100% one time after I filled her up to the top past a few clicks.

I ultimately took it to the dealer to sort, but they also recommended never filling past the clicks when the pump shuts off. It’s been fine since and I never go past the third click now with the pump nozzle fully in. I subsequently found a test in Diagbox that can be used to check the levels, but is a bit Carlos Fandango and requires a certain fuel quantity to be added at a certain level. Too much of a faf, but never had a problem since I observed the recommendation. I believe it may also state this in some owners manuals I have seen if memory serves - about not overfilling.

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GiveMeABreak
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Re: Fuel Gauge

Post by GiveMeABreak » 03 Apr 2019, 20:32

Ok, as promised, here is the technical explanation for your Xsara Picasso as to how the fuel reading is displayed and how this is calculated at both ignition on and when driving:

Phases of operation: When the ignition is switched on.
The instrument panel compares the last fuel level displayed with the gross level indicated by the fuel sender unit (variable resistor fitted with a float).
If there is a significant difference, the gross level information is displayed, otherwise the last fuel level displayed remains.

Phases of operation: When driving.
  • The fuel sender unit is no longer used.
  • The engine management ECU supplies the fuel flow information to the BSI.
  • The BSI encodes this information in a VAN frame.
  • The instrument panel takes this consumption information into account to calculate the fuel level.
  • The instrument panel sends this level to the BSI via the VAN network.
Special cases: Low fuel warning.
Below a certain sender unit value, the instrument panel sends the minimum fuel information to the BSI via the VAN in addition to the fuel level in order to warn the engine management ECU.
In addition, the instrument panel displays the warning message : "LOW FUEL WARNING". The warning lamp V17 is illuminated.

This is what is supposed to be in the tank, according to the segments lit:

"V" in the table relates to the amount of fuel
Picasso Fuel.PNG
SegmentHV17: WarningJKL
LitresV Greater or Equal to 0V Less Than 5V Greater or Equal to 6,5V Greater or Equal to 13,5V Greater or Equal to 20
SegmentMNPQR
LitresV Greater or Equal To 26,5V Greater or Equal to 33,5V Greater or Equal to 40V Greater or Equal to 46,5V Greater or Equal to 53,5

Subsonicnat
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Re: Fuel Gauge

Post by Subsonicnat » 03 Apr 2019, 23:16

ERRRR,, RIGHT OK.....
Thank you.

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GiveMeABreak
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Re: Fuel Gauge

Post by GiveMeABreak » 03 Apr 2019, 23:19

You did ask :rofl2:

Basically it is saying that with the ignition on, it compares the level of fuel the fuel gauge in the tank says is there against what the last level on the dashboard fuel display says. If it is about the same it sticks with the last level on the dashboard; if it is significantly different, it uses what the actual sender in the tank says is there.

When driving, the sender unit in the tank is not used. The injection ECU measures the fuel consumed as you are driving against the level on the dash as calculated using the engine ECU and the BSI.

The next time the vehicle ignition is switched on, it starts the same operation again.

The level of the road and the angle the vehicle is leaning can also affect the levels displayed.

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Re: Fuel Gauge

Post by Subsonicnat » 05 Apr 2019, 09:36

Thank You for the DEscription Marc,
eyes rolling ,lol..
why make it so darn complicated,if it isn't broken why fix it.
The latest aircraft fiasco proves that,too much going on,it hasn nothing to do with emmisions has it. Will see how it behaves when fuel statrs dropping again.

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myglaren
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Re: Fuel Gauge

Post by myglaren » 05 Apr 2019, 11:28

It does seem like a solution to a non-existent problem.
Probably had some functionality unused it the BSI so shoved that nonsense in to look like they were doing something.

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white exec
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Re: Fuel Gauge

Post by white exec » 05 Apr 2019, 12:01

:shock: :shock: #-o
This just leaves me speechless.
As if real-time display of tank contents wasn't good enough!
"I know, let's digitize this...Then we can look busy next week..." 8-)

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GiveMeABreak
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Re: Fuel Gauge

Post by GiveMeABreak » 05 Apr 2019, 12:13

:rofl2: Come on chaps this is PROGRESS isn't it! :rofl2:

It's another reason why I am uber dubious about MikeT's 70MPG!!!! :-D