Fuel gauge inaccurate

[guest3169]

I have a Jazz 1.4 CVT, which is a lovely car apart from the fuel gauge. When this reads empty, and the 'miles to go 'indicator is near zero, there is still 8-9 litres of fuel in the tank. I can never add more than 33 litres to an 'empty' tank, and my max range is 300 miles instead of 400. When the tank is full the gauge is accurate and 'miles to go' is 400+, but it gradually gets worse as the tank empties. I reported this to my dealer at the first service, but they did nothing about it.

Is this a common problem, and has anyone had it fixed?

[Ozzie]

Theres a few threads on here about this, so it seems that theres 7-8 litres left when the miles to go shows 0, it seems that we can't be trusted to refill the car at actual 0 

Ozzie

[culzean]

It's not only Honda, this 'reserve' will apply to pretty much every modern car - with the increasing distance between garages it may be no bad thing (and don't forget - Honda also sell cars in countries like Australia - where the nearest garage can be a hundred miles away).

My mates big BMW motorbike also has a pretty hefty reserve when the gauge shows '0'

[guest3169]

It seems something of a coincidence that amount of the 'reserve' coincides almost exactly with the amount of fuel the handbook says is present when the low fuel light comes on (ie. 7.9l). I suspect that Honda can't measure below this amount so gives up.
A reserve of 20% of the tank capacity seems excessive, especially as it amounts to 70-80 miles of travel.

[eljuero]

Ahh, Honda didn't find any solutions to this problem.

2009 I got responce from local Honda service that everything is according to the book though they were surprised. They said that this is just Jazz specialities (?). And bla bla bla as usually ... the argument that
the car was sold to me with the feature "expected mileage", which comes handy when the tank is almost empty so I can expect that feature to work, was ignored.

I guess the problem is in the specific shape of the tank. I wonder though, why is the mpg info pretty accurate all the way.

Use simple math, I do. But yes, psychological effect is bigger some times even when you know

[guest2765]

my car is rarely down to petrol light on emptyness, but ive ran it for a few days on what i assumed were fumes, but seems my 02 GD also has about 2 galleons left in it when the petrol gauge says the tank is empty.. i wouldnt worry about it if i was you, just think of it as an emergency reserve for....for example incase people panic buy petrol and leave stations empty

[culzean]

The majority of cars are driven by people who never look under the bonnet and haven't a clue how the engine works etc.  I am more than happy that if my wife was driving when the tank shows empty that there is still about 80 miles left - this is much better than her getting stranded because she only noticed how low the fuel was when the light started flashing and the nearest open 24hr garage (could be at night)  is 40 or 50 miles away. 

For the people who do want to know,   I am sure there is some third party system that can be added to a car to give the remaining fuel and mileage down to 2 decimal places - but car makers have to cater for everyone and will always err on the side of caution.

The MPG readout on most modern (injected) cars is derived from the ECU which knows the length of time that the injectors are open for and how many times per second they open etc.  To say that Honda don't know how much fuel is left is pretty insulting to their engineers,  but when the tank gets down to a couple of gallons the swilling around of the fuel when car is going up and down hills or similar can alter the level quite a bit and may allow air into fuel intake, it can also stir up sediment etc - it's just not worth letting the fuel get that low.

[eljuero]

Thank you for that but how do you explain why the future "expected mileage" is correct only first km/miles; when the tank is halfway the data is already obviously incorrect and it gets worse.

Maybe you know if other Honda models suffer from the same thing?

[culzean]

The expected mileage after half a tank is probably wrong for the same reason that the first half of the tank seems to last longer than the second half - because the needle hits zero when there is still about 7 to 8 litres left.

I have checked from full to half a tank and it is consistently around the 20 litre mark.  Which means that half is almost exactly half !  But the second half (according to when gauge shows zero) is only about 12 to 13 litres - (but the second half of tank still contains 20 litres or so ) and the rest is deliberately left by Honda as a 'reserve'.

This is not bad engineering - it is safe engineering - it means that no-one (unless they want to) should ever  be left with insufficient fuel to not  be able to reach the next petrol station when the light flashes or 'expected mileage' display shows zero.

[guest1521]

IMO it's good that Jazz has a generous reserve. Apart from the benefits of personal 'safety' and convenience, as a car ages there can be a little undesirable 'sediment' and condensation/water in the bottom of the tank and, though the fuel filter should deal with it, for ongoing reliability I'd prefer not to suck any up. I agree with culzean.

[eljuero]

I was told that its the same with Civic 8. generation. 
You are probably both wright, I just wonder why Honda's trip computer even has that feature then.

[John Ratsey]

I agree that it is disconcerting that there's so much fuel remaining when on "empty". A sensible compromise would be for the mechanical gauge to show empty with some reserve but the computer to show its best estimate of miles remaining. I've noticed that once the gauge gets down to around 1/4 the miles remaining on the computer decrease much faster than the miles travelled.

It's not a fault as such but some logic that I don't completely agree with.

John

[Ciaran84]

What irritates me is that my fuel gauge doesn't start to move off full for about 50 miles after i fill up, then seems to drop quickly until it drops below a quarter. Makes it awkward to judge consumption/efficiency...

[chrisc]

There is a flag on the OBD-II software that lets the reading of the gauge be adjusted + or - in 0.5 percentage increments, but there is a warning to leave it alone unless the sensor has been rewired or changed

[guest3170]

Those clever folks at Honda...  despite building in the safeguard of pessimistic fuel level & remaining distance readings they also remembered to tell the same computer to give an optimistic fuel economy reading