I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with limited
resolution but even so that was strange. Stranger still was that the
'miles to go' figure didn't change either, it stayed on about 90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much. The only difference today was that I
parked at the pump on the 'wrong' side because the garage was busy, and
wasn't close enough to get the nozzle in fully and it was upside down.
The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated. Any ideas?

It's an 04 Citroen Xsara Picasso.

--
Cheers
Clive

On Sun, 26 Jan 2020 15:39:23 +0000, Clive Arthur wrote:

I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with limited
resolution but even so that was strange. Stranger still was that the
'miles to go' figure didn't change either, it stayed on about 90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much. The only difference today was that I
parked at the pump on the 'wrong' side because the garage was busy, and
wasn't close enough to get the nozzle in fully and it was upside down.
The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated. Any ideas?

It's an 04 Citroen Xsara Picasso.

I got a similar effect when I filled up my AdBlue tank. It righted itself
a mile or two leter, though.

--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

On 26/01/2020 15:57, ARW wrote:
On 26/01/2020 15:39, Clive Arthur wrote:
I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with
limited resolution but even so that was strange.Â* Stranger still was
that the 'miles to go' figure didn't change either, it stayed on about
90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much.Â* The only difference today was that
I parked at the pump on the 'wrong' side because the garage was busy,
and wasn't close enough to get the nozzle in fully and it was upside
down. The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated.Â* Any ideas?

It's an 04 Citroen Xsara Picasso.


I am interested.

The hire van that I used to move a piano never altered the fuel gauge or
the "miles to go" range on the dash despite shoving 4 gallons of fuel
into it from fuel cans.

The range/mpg will be computed from the mileometer and fuel used. The
fuel used is calculated by the ECU by how many injections and how big
they were. So as you drive it knows how far and how much fuel used. It
can then use that for mpg. Remaining range is updated as it knows how
much it had and how much is being used.

The initial range comes from how much in the tank and how much is used.
i.e. tank reads full, car sets max possible range from known last mpg.
As you drive, fuel use is calculated and mpg/range updated. Next time
level changes, i.e. sender indicated next level, 9/10ths full, range is
re-evaluated based on current mpg and known remaining fuel.

If you add fuel but not enough to cause the sender to move to the next
level, the range calculations will not know you have added more fuel so
the range wont increase but will keep decreasing as you drive. The range
will re-calculate at the next time the sender level changes, probably
upwards.

What you are really saying then is that its a bodge in the first place to
avoid a finer grained measurement of the fuel level in the tank. Bring back
analogue.
Brian

--
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This newsgroup posting comes to you directly from...
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"mm0fmf" wrote in message
...
On 26/01/2020 15:57, ARW wrote:
On 26/01/2020 15:39, Clive Arthur wrote:
I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with limited
resolution but even so that was strange. Stranger still was that the
'miles to go' figure didn't change either, it stayed on about 90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much. The only difference today was that I
parked at the pump on the 'wrong' side because the garage was busy, and
wasn't close enough to get the nozzle in fully and it was upside down.
The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated. Any ideas?

It's an 04 Citroen Xsara Picasso.


I am interested.

The hire van that I used to move a piano never altered the fuel gauge or
the "miles to go" range on the dash despite shoving 4 gallons of fuel
into it from fuel cans.

The range/mpg will be computed from the mileometer and fuel used. The
fuel used is calculated by the ECU by how many injections and how big they
were. So as you drive it knows how far and how much fuel used. It can then
use that for mpg. Remaining range is updated as it knows how much it had
and how much is being used.

The initial range comes from how much in the tank and how much is used.
i.e. tank reads full, car sets max possible range from known last mpg. As
you drive, fuel use is calculated and mpg/range updated. Next time level
changes, i.e. sender indicated next level, 9/10ths full, range is
re-evaluated based on current mpg and known remaining fuel.

If you add fuel but not enough to cause the sender to move to the next
level, the range calculations will not know you have added more fuel so
the range wont increase but will keep decreasing as you drive. The range
will re-calculate at the next time the sender level changes, probably
upwards.

On 26/01/2020 21:07, Brian Gaff (Sofa 2) wrote:
What you are really saying then is that its a bodge in the first place to
avoid a finer grained measurement of the fuel level in the tank. Bring back
analogue.
Brian


No, I'm telling you how it functions. If you want to apply some personal
view you're welcome to. But it's just an opinion and opinions are like
arseholes, everyone has one. Given that the low resolution gauges
typically have a range read out and that underestimates the range then
there is no real need to have a fine resolution.

In reality, drivers learn to interpret the fuel gauge in a short amount
of time if they drive the same car often. So the gauge ends up
essentially saying "fill up real soon sunshine if you don't want to
spoil your day" or "everything in the garden is rosy, go for it".

On 26/01/2020 15:39, Clive Arthur wrote:
I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with limited
resolution but even so that was strange.Â* Stranger still was that the
'miles to go' figure didn't change either, it stayed on about 90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much.Â* The only difference today was that I
parked at the pump on the 'wrong' side because the garage was busy, and
wasn't close enough to get the nozzle in fully and it was upside down.
The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated.Â* Any ideas?

It's an 04 Citroen Xsara Picasso.

I've had the same thing with a Zafira on more than one occasion. It's
righted itself either later in the journey or the next time I have used it.

SteveW

On 26/01/2020 15:39, Clive Arthur wrote:
I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with limited
resolution but even so that was strange.Â* Stranger still was that the
'miles to go' figure didn't change either, it stayed on about 90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much.Â* The only difference today was that I
parked at the pump on the 'wrong' side because the garage was busy, and
wasn't close enough to get the nozzle in fully and it was upside down.
The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated.Â* Any ideas?

It's an 04 Citroen Xsara Picasso.

seen this before. what you see on te dash is heaavily damped to prevent
the numbers going up and down and frightening punters but there is an
override that will instantly register large changes.

It should sort itself out.




--
"First, find out who are the people you can not criticise. They are your
oppressors."
- George Orwell

On Sun, 26 Jan 2020 16:37:40 +0000, mm0fmf wrote:

If you add fuel but not enough to cause the sender to move to the next
level, the range calculations will not know you have added more fuel so
the range wont increase but will keep decreasing as you drive. The range
will re-calculate at the next time the sender level changes, probably
upwards.

The fuel gauge on the dash will in all probability have no direct electrical
connection to the sender, instead it could be driven from an ECU output. The
dash computer may even just sniff a CANBus signal representing that fuel level,
interpret that and then drive a bargraph, a stepper motor or a moving coil
device with a pointer on the end.

The actual level from the fuel tank sender might be digitised to 8 bits or 256
levels, or even more, so the possibility of putting say a litre of fuel in a
tank holding 60 litres and the actual level measured by the ECU not changing is
pretty small.

But the gauge itself might only be driven to one of only say sixteen discrete
levels. In the past they were heavily damped, now that is effectively done in
software.

The initial range after refuel is calculated from the actual measured fuel level
and the rate of usage from immediately before the refuel, and updated with the
actual usage when the engine starts. If you coast down hill for many miles
before refuelling your range can be drastically overstated.

Similarly if you dispense small amounts (maybe 3 litres) of fuel from a can into
the tank, the range instantly updates on an ignition on event without the
vehicle starting and turning a wheel, even after it has been sat unused for
several months.

But as ever your specific vehicle range measurement techniques can vary.

--

On Monday, January 27, 2020 at 8:31:07 AM UTC, The Natural Philosopher wrote:
On 26/01/2020 15:39, Clive Arthur wrote:
I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with limited
resolution but even so that was strange.Â* Stranger still was that the
'miles to go' figure didn't change either, it stayed on about 90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much.Â* The only difference today was that I
parked at the pump on the 'wrong' side because the garage was busy, and
wasn't close enough to get the nozzle in fully and it was upside down.
The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated.Â* Any ideas?

It's an 04 Citroen Xsara Picasso.

seen this before. what you see on te dash is heaavily damped to prevent
the numbers going up and down and frightening punters but there is an
override that will instantly register large changes.

It should sort itself out.




--
"First, find out who are the people you can not criticise. They are your
oppressors."
- George Orwell

Fuel tanks on cars look more like some internal body organ out of ones gut. The very irregular shapes make them hard to measure the contents.

Generally I find they are forgiving and will go a little further than anticipated except for one humpty dumpty Hillman Hunter I had which would stop dead once they needle hit zero

On 26/01/2020 15:39, Clive Arthur wrote:
I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with limited
resolution but even so that was strange.Â* Stranger still was that the
'miles to go' figure didn't change either, it stayed on about 90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much.Â* The only difference today was that I
parked at the pump on the 'wrong' side because the garage was busy, and
wasn't close enough to get the nozzle in fully and it was upside down.
The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated.Â* Any ideas?

It's an 04 Citroen Xsara Picasso.


That model commonly suffers from failure of the sender device.

Neigbour has been asked to fix a couple, and when he discovered
the price of the replacement sender unit, the owners decided to
just use the trip meter to warn them when to refuel.

On Sun, 26 Jan 2020 16:37:40 -0000, mm0fmf wrote:

On 26/01/2020 15:57, ARW wrote:
On 26/01/2020 15:39, Clive Arthur wrote:
I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with
limited resolution but even so that was strange. Stranger still was
that the 'miles to go' figure didn't change either, it stayed on about
90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much. The only difference today was that
I parked at the pump on the 'wrong' side because the garage was busy,
and wasn't close enough to get the nozzle in fully and it was upside
down. The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated. Any ideas?

It's an 04 Citroen Xsara Picasso.


I am interested.

The hire van that I used to move a piano never altered the fuel gauge or
the "miles to go" range on the dash despite shoving 4 gallons of fuel
into it from fuel cans.

The range/mpg will be computed from the mileometer and fuel used. The
fuel used is calculated by the ECU by how many injections and how big
they were. So as you drive it knows how far and how much fuel used. It
can then use that for mpg. Remaining range is updated as it knows how
much it had and how much is being used.

The initial range comes from how much in the tank and how much is used.
i.e. tank reads full, car sets max possible range from known last mpg.
As you drive, fuel use is calculated and mpg/range updated. Next time
level changes, i.e. sender indicated next level, 9/10ths full, range is
re-evaluated based on current mpg and known remaining fuel.

If you add fuel but not enough to cause the sender to move to the next
level, the range calculations will not know you have added more fuel so
the range wont increase but will keep decreasing as you drive. The range
will re-calculate at the next time the sender level changes, probably
upwards.

That sounds like a very shoddy design. Is it a Renault? My fuel guage moves more quickly for one half of the guage than the other (unfortunately I can never remember which), as for the miles to running out, it's complete and utter nonsense. When I fill the tank it says something like 450 miles. I can only do 300 on a full tank.

The only useful thing that French piece of **** ECU does is show me a very accurate average speed, which means when driving along a motorway with SPECS cameras, I can get stuck behind something, then drastically exceed the speed limit for the rest of that section, while keeping my average speed legal.

On 26/01/2020 16:37, mm0fmf wrote:
On 26/01/2020 15:57, ARW wrote:
On 26/01/2020 15:39, Clive Arthur wrote:
I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with
limited resolution but even so that was strange.Â* Stranger still was
that the 'miles to go' figure didn't change either, it stayed on
about 90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much.Â* The only difference today was that
I parked at the pump on the 'wrong' side because the garage was busy,
and wasn't close enough to get the nozzle in fully and it was upside
down. The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated.Â* Any ideas?

It's an 04 Citroen Xsara Picasso.


I am interested.

The hire van that I used to move a piano never altered the fuel gauge
or the "miles to go" range on the dash despite shoving 4 gallons of
fuel into it from fuel cans.

The range/mpg will be computed from the mileometer and fuel used. The
fuel used is calculated by the ECU by how many injections and how big
they were. So as you drive it knows how far and how much fuel used. It
can then use that for mpg. Remaining range is updated as it knows how
much it had and how much is being used.

The initial range comes from how much in the tank and how much is used.
i.e. tank reads full, car sets max possible range from known last mpg.
As you drive, fuel use is calculated and mpg/range updated. Next time
level changes, i.e. sender indicated next level, 9/10ths full, range is
re-evaluated based on current mpg and known remaining fuel.

If you add fuel but not enough to cause the sender to move to the next
level, the range calculations will not know you have added more fuel so
the range wont increase but will keep decreasing as you drive. The range
will re-calculate at the next time the sender level changes, probably
upwards.







I would have expected 4 gallons to have moved the sender unit.

However it was a hire van and I only used it once.

My car will pick up the addition of 1 gallon of fuel from a can.

As to the range:-) Both the van and the car do weird and wonderful
things with that. I still have not decided if they recalculate after
time or mileage.

Both can knock 20 miles off the range after either a short steep up hill
run or just a bit of speed but then adds 20 miles back on as you either
go down the other side of the hill or take your foot off the accelerator
when you hit the 50MPH roadworks.

The car ALWAYS knocks 5 miles off the range when you start it up. So in
theory 120 starts of the engine should use a full tank of fuel.




--
Adam

On 26/01/2020 15:39, Clive Arthur wrote:
I put some petrol in the car today , not much about 10 litres.

It didn't seem to register on the gauge, that's a bargraph with limited
resolution but even so that was strange.Â* Stranger still was that the
'miles to go' figure didn't change either, it stayed on about 90 miles.

I've never seen that before but I usually put more in, albeit
infrequently, it's not used much.Â* The only difference today was that I
parked at the pump on the 'wrong' side because the garage was busy, and
wasn't close enough to get the nozzle in fully and it was upside down.
The petrol did go in the car and not on my feet.

I had assumed that the fuel gauge was a float on an arm jobbie, but
maybe it's more complicated.Â* Any ideas?

It's an 04 Citroen Xsara Picasso.

The next day the 'miles to go' was still 90 miles and I commenced my 100
mile round trip journey.

Up till about 30 miles, mostly motorway, the miles to go crept up to 130
miles, then started to decrease. Of course, this figure does often
increase a little depending on the changing MPG, but this amount was
quite unusual, as if I was being topped up by an invisible tanker as I
drove, which I suppose can't be ruled out.

Anyway, I got home with 80 miles left which is about right for that journey.

I do like that old car. One of the passenger doors stopped locking for
about a year, didn't matter much, then it fixed itself at the same time
as the various dashboard messages decided to change to German.

--
Cheers
Clive