C5 fuel gauge problem.

[demag]

We were driving home from our weekly pensioner's special lunch today when there was a warning bong from the dashboard and a low fuel warning. The car has half a tank of diesel and has only done 247 miles. It usually does between 4-500 miles around town.

Is it ok to short the sender wire to earth as we used to on pre ecu cars, or is that a no no now? I want to eliminate sender or gauge.

[Gibbo2286]

I wouldn't recommend it Dave, better safe than sorry on this multiplexed stuff.

[xantia_v6]

The safest and easiest thing to do first is to fill it up and see how much it takes.

[wheeler]

Do a BSI reset first, this normally sorts out fuel gauge glitches. The sender is only used to read the fuel level on initial start up anyway, the injection ECU then calculates fuel usage as your driving.

[demag]

Ah I didn't realise that. Strange beasts aren't they. I'll pop out in a bit and try it.

[Hell Razor5543]

Ah I didn't realise that. Strange beasts aren't they. I'll pop out in a bit and try it.

Nah, they are Citroens, not strange at all by that fact!

[Peter.N.]

I would also go for a BSI reset. The first one I bought ran out of fuel on the M5 on the way home although it was showing some and that cured itself after I had disconnected the battery - didn't know anything about BSI resets in those days.

Peter

[demag]

The bsi didn't have any effect so I popped up the road and brimmed the tank. Voila its working! But the amount I put in wouldn't have filled the tank from empty so I appear to have a problem evolving. I put less than 10 gallons in to fill it and the gauge is now right over on full. I'll keep my eye on it.

[ekjdm14]

Ah I didn't realise that. Strange beasts aren't they. I'll pop out in a bit and try it.

Nah, they are Citroens, not strange at all by that fact!

Indeed not, Black & White both also only respond immediately to the sender on initial switch-on. Moving the float from one extreme to the other with the ignition on has no immediate effect on the gauge reading & after 45 seconds the needle appeared to have moved a hair, but it may have been my perception.

Fine when all is well & makes for a much steadier reading but if you were to develop a leak you may never realise until you ground to a halt with an empty tank... Stranger still as both are XUD cars with no engine ECU to calculate usage, all I can guess there is that the instrument cluster electronics estimate usage based on speed/revs/time... Yet I distinctly recall AX gauges of the same era were a little too sensitive to the float position and even gentle cornering could provoke 1/4 of a tank's variation "Because Citroen"

[xantia_v6]

Xantia fuel guages don't connect to the ecu. They just get the signal from the sender but react very very slowly to changes in level.