Miles To Go Till Fill-Up - Which Reading To Trust..?

[trufflehunt]

On my car, the fuel level warning light comes on before the needle reaches the red zone
on the gauge. Below the first white bar, and approaching the red bit.
I usually put more diesel in within about 20 miles after that.

The type C MFD display shows the number of miles to go before fillup required.

The gauge or the computer, which to trust ?

And if I get it wrong, and I run out, does the HDI take care of it all and start up, or do I have to get
my head under the bonnet and do some priming?

[gumby6371]

406 fuel gauges are notoriously crap but they tend to be consistant in their crapness so you need to find out when the light comes on.
If you brim the tank as soon as possible when the light comes on it will give you an idea of how much fuel you have left, work on roughly 70 litres from completely empty.
70 - fuel in = red light level
I usually get about 55 litres to the first click at the pump which means I have just over 3 gallons left by my maths.
The Siemens set up will give you a priming bulb incase you do run out but I believe they only fitted them to 90's so for 110's it's a case of put fuel in then cycle the ignition a few times to let the lift pump prime things as per a fuel filter change and away you go.

I always fill up at red light which gives you an idea of average miles to a tank so you can spot when somethings wrong.

Remeber that the crap from the bottom of your fuel tank wont do you pump and injectors any good so avoid running out if at all possible.

[benczuk]

I have managed to get mine to read zero miles range on the MFD but still driven a couple of miles before finally finding a petrol station.

If I was writing the software for the computer I would certainly make it show 0 a bit before it ran out... but who knows what the french would do (probably the reverse just to catch you out! )

[Rolebama]

I vaguely remember reading somewhere that the computer is based on the red light coming on. So when the computer reads zero, there should always be enough to get you to a refill.
(It may have been in some AA published literature somewhere.)

[trufflehunt]

I vaguely remember reading somewhere that the computer is based on the red light coming on. So when the computer reads zero, there should always be enough to get you to a refill.
(It may have been in some AA published literature somewhere.)

Yes, that seems logical.
However, light came on yesterday evening, with 90 miles left on the computer.
Think I'll have to take deep breath and do a complete fillup to the brim to check.

Thanks chaps.

Andrew

[PeterN]

I have always reckoned that there is a good gallon or more left when the light comes on, in fact I did about 100 miles in my XM with the light on, but - since I had the water in electrics problem with the 406 it runs out about 10 miles after the light comes on although it is still showing between 1/4 full and empty, as I found to my cost on a busy and dangerous stretch of the A30 in Cornwall. Last time the light came on my wife filled it up and it took 72 litres, so there wasn't much left.

Peter

[Doggy]

I've had the light come on with anything from 23 to 55 miles to go, (it's supposed to come on at 6 litres left).
Changes in your instantaneous consumption after the light comes on can have a disproportionate effect on the range number - I've seen it go up, or go to ---- pretty quickly.
I have done 20 miles or more after the ---- indication and never run out. Must've come close on occasion, as I have mananged to get 78 litres in once.

If you do run out, put some fuel in the tank, turn the ignition on for 5 seconds and off again so the lift pump refills the fuel filter, then start it - they're self bleeding*. Don't crank the engine repeatedly with no fuel, this can damage your HP pump.

*Unless it's a later HDi 90 with a Siemens fuel system, in which case prime it with the bulb.....

[steve_earwig]

Remeber that the crap from the bottom of your fuel tank wont do you pump and injectors any good so avoid running out if at all possible.

The pump draws from the bottom of the tank all the time anyway, the worst it could do is pull in anything floating on top of the fuel...