How Erratic Is Your Fuel Gauge?

[Unregistered_User]

I'm sure you'll manage to say what you mean ^^^

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Regards,

Jamie

[Continunity]

id be happy to get the light coming on at 375 miles, mine no matter how i drive always ends up at 300 ish. but hay its always fun to drive

[Vyker]

dont get me wrong, im not moaning about MPG, i know i drive it too aggressivley and wasteful, but its fun.

its just im sure you dont get your light come on at 1/4 tank!.... do you?

[Guest inicol63]

I am only getting around 300-350 miles to the tank (is200se) however it is a auto so guess that not too bad.

I managed around 300 miles per tank on my SC430 around 23 per gallon.

With only 5 miles difference between each car per gallon i much perfer to drive the SC430.

Never seen the petrol light on, as i never let the car go below 1/4 tank.

Guess dont like walking to the garage with a can

Ian

[Vyker]

Right.. hello again..

Firstly sorry to management for resurrecting an old topic.

Secondly, I think my problem here has fixed its self, I have no idea how, but I have come up with some random guestimates.

My first thought.. is that I often find myself driving with a full passenger load, more often then not, 3 big blokes sat in the back seats, and with all that weight, could it have jigged the contacts under the seat base? [as Mat mentioned earlier in the topic]

My second thought... is that the previous owner used to drive only 4miles per day in 2 stints. 2miles to goto work, and 2miles back, so he never really used to fill it up more then once every 3months.

Since I bought it off him, I fill it up once a week.

As the ECU "learns" our driving style, could the fuel ECU have set itself to not check on the status of the tank quite so regularly, and now since Ive done many miles it has learnt to check more often under my driving style?

Does the ECU have a setting for "Check fuel tank"? "on startup/once a week/every 100miles" ?

Both very random thoughts I know, but if anyone of you think any of this might be the reason why my needle is now very accurate then please let me know, also let me know its is all nonsense :P

Thanks

Vyker

[eXOBeX]

Just to throw a spanner in the works, my gauge does this too, but the other way.

Even though I'm running on LPG, the petrol gauge will continue to fall gradually, but every so often it seems to "realise" that I've used next to nothing, then jump back up again. The jump is typically a quarter of a tank. Even the amber fuel warning light isn't immune to this, when the gauge jumps back up (which it will do whilst I'm on the move) the light goes back out.

My guess is that it only checks and redisplays the actual capacity every so often, unless there's a big jump in the reading (in other words you've put some more in), in both cases the actual fuel level then gets displayed. In between, it's just guessing how much has gone based on the same figures your trip computer (if you have one) would use.

[SHAHZ]

id be happy to get the light coming on at 375 miles, mine no matter how i drive always ends up at 300 ish. but hay its always fun to drive

Same here!!

[Sagitar]

My guess is that it only checks and redisplays the actual capacity every so often, unless there's a big jump in the reading (in other words you've put some more in), in both cases the actual fuel level then gets displayed. In between, it's just guessing how much has gone based on the same figures your trip computer (if you have one) would use.

That sounds highly unlikely. I don't know the details of your fuel gauging system, but typically there is a "sender" (more than one if the tank shape is complicated) of some kind in the tank - at its simplest this may be a float connected to a potentiometer giving a change in voltage as the float position changes - this voltage drives the indicator on the dashboard. To stop the dashboard indicator from swinging there will be some kind of damping arrangement - maybe mechanical on the indicator itself and a capacitor across the circuit to smooth out the voltage changes.

There will be a relay that trips the warning light on and off as the voltage level passes a threshold so it will be susceptible to exactly the same errors as the dashboard indicator.

Modern vehicles may have more sophisticated arrangements for transferring the information from the "sender" to the indicator, but the operating principles remain the same and the information is transferred continuously. Even if the use of a data bus and multiplexing results in discrete data packages, the switching frequency is relatively high and effectively the data are transferred in an unbroken stream.

Several of the components in the system, including simple wiring connections that oxydise, could account for what you are seeing and I would look first for simple solutions (like cleaning connections) . . . . . :)

[dazz32]

Mine only illuminates when it heads right near the final line!

Same here.

What sort of mileage do you get from a tank Jamie?

I'm lucky to get around 300 - but the usual factors obviously take a stance - driving manner, weather etc etc.

But yeah, around 300ish.

J

Thats what i get jamie about 310-330 out of a tank full of 95ron thats until the light comes on ( last white line on the fuel gauge).

What about reseting the ECU would that make a difference to getting more fuel etc? i guess also the state of the fillters would have an affecton the MPG?

[rig-pig]

thats what i was getting daz i put in a K&N pannel filter some new Denso IR plugs and reset the ECU now getting 350-400m out of a tank o 95ron next if a new fuel filter