Citroen Xsara Low Fuel Warning

[xsaras4ever]

Hello to all.

The car in question in a Phase 2 Citroen Xsara 1.4hdi - - - - yes - - - 1.4hdi.

We havn't been using it much recently and have allowed it to run low on fuel a few times.

The little orange warning light comes on and you have to put about 35litres of fuel in to it to get the needle to move and the warning light to go off.

We thought it might be the fuel sender in the tank so we replaced it but it didn't solve the problem.

We have since learned that its a design issue - it doesn't really monitor the actual fuel in the tank in the old-fashioned way. It reads it and calculates how many km are left and reduces the fuel needle according to km covered.


Our question is...............is there any way to kickstart the system to give a correct reading. We tried disconnecting the battery - turning on the ignition and then re-connecting the battery to see if the ecu would re-read everything. This did not work.

Yeah - sure - some clever clogs will suggest putting more fuel in it..........

[GiveMeABreak]

Dave - pop up the VIN as this is different to the 2.0 one I have for you it seems.

[xsaras4ever]

Hello , sorry - we are not DAVE.

We disconnected the battery again last night and re-connected it this morning.

We started the car and the fuel level needle shot up to just below half and the orange light did not appear.

We would prefer to know how much fuel we have as compared to the small inconvenience of re-setting the time on the clock.

Thanks for the interest

Regards

Franc & Wendy

[GiveMeABreak]

Apologies - I don't know where I got 'Dave' from - I was probably on another planet at the time

Do you have the VIN for this particular vehicle?

[xsaras4ever]

No probs.
Vin is VF7**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

Edit: In light of the VIN I now have - the information I previously posted is different, so I have changed everything to reflect the changes in the year for the 2004 model:

So this is how the fuel gauge information is displayed and not quite as you were told....

When the ignition is switched on:
The instrument panel receives the fuel gauge information and uses a static law (vehicle stopped) to calculate and display the level of fuel.

Whilst Driving:
When speed is greater than 3 km/h, the instrument panel still receives the information from the fuel gauge, but uses a dynamic law to calculate and display the level of fuel.
N.B. : The dynamic law uses the fuel flow information coming from the engine ECU via the CAN network.

Low Fuel Warning:
The instrument panel transmits the min. fuel information to the BSI via the Comfort VAN network.
The BSI then manages:

• The diffusion of this information on the CAN network
• The control of the audible warning on the Com 2000 (pre-alert sound no. 2)
• The lighting of the warning lamps on the instrument panel

Fuel	Capacity ( litres)	Resistance (ohm)
Petrol	7.5	255
Diesel	10	239

N.B.: The gauge needle continues to fall, it cannot rise.
N.B.: The alert warning lamp no longer flashes . Once the warning lamp is lit, it remains lit.

Indication	P1	P2	P3	P4	P5	P6	P7	P8
volume ( litres)	54	52	41	27	14	11.5	9	0
Resistance (ohm)	35	49	104	159	220	231	247	-
Resistance (ohm)	Full	Full	75	50	25	Lamp Lit	Lamp Lit	Empty

N.B.: Take a threshold of 400 ohms to detect an open circuit.

[xsaras4ever]

Hello and thank you for the very excellent reply.

As the needle went to just below half when we re-connected the battery, we would assume that we had somewhere between the 14 and 27 litres.

Therefore, previously when we turned on the ignition, we had enough fuel to generate enough rsistance to move the needle and turn off the low warning light.

When the ignition is switched on:
The instrument panel receives the fuel gauge information and uses a static law (vehicle stopped) to calculate and display the level of fuel.

So are we correct in saying that we have a fault somewhere ?

[GiveMeABreak]

I would say if the warning light is coming on at half a tank you have a fault for sure. It should only be coming on at the 10 litre 'ish' level.

But when you have been disconnecting and reconnecting the battery - are you following the correct procedure (BSI reset effectively)? Not doing so can lead to all sorts of electrical issues.

[xsaras4ever]

Hi Marc.

Just to clarify.

In normal driving the car is fine. The fuel needle operates just great. Let it go down, put some fuel in and it rises again.
It is only when we let it go to almost empty and the fuel warning light comes on - then it all seems to freeze.

Yep , we are aware of the BSI reset procedure - open window , lights on and off etc....

We havn't done this - we just disconnected the battery one evening and reconnected it the next morning ----- just the one time.

Thanks again

[dave_xsara]

Apologies - I don't know where I got 'Dave' from - I was probably on another planet at the time

Probably me!
I had previously problems with the fuel gauge on a 2.0HDi Xsara giving inaccurate readings.

What I done was to remove the pump/sender unit from the tank dry it off and then clean the fuel sender circuit with electrical cleaner. I then put a multimeter across the pins for the sender and was able to see that the resistance varied from 10 Ohms (full) to 310 Ohms (empty) as I moved the float. It's basically a variable resistor - so easy to check at home. You should be able to find the correct range for the sender from Marc via your PIN. I would suggest though doing what I subsequently done as outlined below.

Once I determined that the sender was working correctly, I then brought it back to the car and sat it on the back seat. I then connected two flying leads from the plug in the harness - only connecting the sender and not the pump itself. I then set the float to its max position and turned on the ignition. Fuel gauge reading - full. Then set the float to its min position. Fuel gauge reading - empty. I then tried a few intermediate readings following the same process and it correlated. Due to the way the fuel gauge works (as previously outlined) you need to cycle the ignition to get the initial reading. It seems to be behaving a bit better now.

Now, as to what bit resolved the problem - I'm not sure. I doubt that all the above steps were required. Possibly unplugging the unit, cycling the ignition, and then re-connecting might suffice. The computer might just need to read an open circuit and then clear its throat. If that doesn't work, take it out and manually move the float as outlined above and see how the gauge responds.

EDIT - Actually, just re-read about your setup and it is a lot different to mine, so not sure if any of it is applicable.

[GiveMeABreak]

Ahh will the real Dave please stand up!

So the resistances are in the table in my previous post for the OPs particular model - these do vary in design and operation between models and years - as I had to retype the info once I had the VIN. so what's posted now is correct for that model.

[xsaras4ever]

Hello again to all and thanks for all the help.

Our first thoughts were that it was the sender.
We took out the original sender , moved the float up and down manually - no reaction with the needle.

We bought another sender, connected it and moved the float up and down manually - no reaction either. We fitted the replacement anyway.

It was after that that we disconnected the battery over-night and the needle adopted the correct position.

Just to introduce a bit of clarity.

1.) Normal driving - needle works fine.
2.) Put fuel in before the warning light comes on - needle works fine
3.) Allow fuel to go low and warning light illuminates - needle stays at bottom and light stays on - need about 30 litres to get it to move.