Fuel Fuel Gauge Errors

[streakybird]

Hi Civinfo'ers

Just went to put petrol in the car and went into the petrol station with 56miles left of petrol, only put in a tenner to top it up, and started the engine only to find the reading at 42miles left...
The ignition key was with me and obviously the engine was turned off!
So i went into the garage with more petrol in than when i topped up and came out!

When you try put petrol in, the metre would only run if petrol is available right... so i didnt just pay a tenner for nothing!!!

Is there a known error??? or should i be worried?

btw... there seems to be no sign of any leaks!!! i dam well hope not anyway!!!

[parsnip]

i suppose the margin of error for the figures would depend on how the current level of fuel is calculated, maybe it's weight? does anyone know?

I'm going to fill up mine later this week hopefully (if the panic buyers havent dried up the pumps) and I'll compare what it says for mpg with actual results

[Dimplyred]

My wifes old 206cc used to do this. If the fuel level was low and I only put £10 in, the guage wouldn't move nor would the trip computer indicate a change in 'miles left' .

It was really annoying.

[scrofts007]

I too had exactly the same issue - about a fortnight ago, I went to my usual haunts, but they were out of deisel - there is an independant garage that is very expensive (£1.32 even then!), so I put a tenner in to get me into town where I could fill up, and the rangefinder didn't change - guess it's to do with the float not moving far enough - or maybe as it wasn't parked level before I started the engine??

[Unknownsoldier]

Mine does that occasionally if I've popped just a bit in, but it also suffers from sudden drop, i.e. it'll go for 100miles without the needle moving, then it'll fall like a stone.... a bizarre gauge, but I wonder if it's odds because of the shape to fit beneath the seats in the front, or the baffles??????

Tom

[Kremmen]

I think there's been previous posts on this where you do need to put a certain amount in for it to register.

I would have thought that £10 would do it though - almost 2 gallons.

[streakybird]

I think it was maybe because i only put in a tenner! I normally never do... I think a tenner does nothing these days! Well anyway i went back to the petrol station and topped up another £20, when i went to switch the engine on, the gauge jumped up to almost a full tank! I assume there was an error there and the tenner has now registered on top of the £20! All is fine now, but not very promising... i was wondering, what happened if it went down to only 20 miles left of petrol, would i have had the warning light come on even though i had put petrol in it, so therefore it would not actually come to a stop due to the lack of petrol??? I could have continued to drive and drive with it registered at zero!!!

[Kremmen]

I think the problem with the Civic is that the fuel tank is not a normal shape that can be measured with a standard 'float' mechanism.

Because the tank is spread out under the floor it must haev another way of trying to gauge how much fuel is in there even when it is sloshing around during driving.

I wonder how deep the tank actually is ? probably only a few inches.

[rmh999]

Originally Posted by streakybird

Hi Civinfo'ers

only put in a tenner to top it up,

There`s your problem...

Gordon took £5
Esso took £1
Garage took £1

You only really got £3 worth of fuel...

[Smarty]

I'm sure I've read somewhere about the tank size and it being very shallow, but I can't remember where - not much help really. Anyway, I had the same "problem" - was worried at first there was a problem with the pump, but I only put a fiver in to keep me going. The trip gauge didn't change, but when I drove off, it started to count down to zero, but only moved a mile for roughly every two miles I drove. I guess it would have got down to zer o at the right time, roughly.

[streakybird]

Originally Posted by rmh999

There`s your problem...

Gordon took £5
Esso took £1
Garage took £1

You only really got £3 worth of fuel...

what utter thieves...

[parsnip]

Well I filled up today and the displayed MPG was 42.9 and actual MPG was 43.4

I filled up with 41.4 litres, so the display was calculating I'd used 41.9 litres

So it was out by 0.5 litres or 1.2%

[parsnip]

Originally Posted by streakybird

Hi Civinfo'ers

Just went to put petrol in the car and went into the petrol station with 56miles left of petrol, only put in a tenner to top it up, and started the engine only to find the reading at 42miles left...
The ignition key was with me and obviously the engine was turned off!
So i went into the garage with more petrol in than when i topped up and came out!

I just had another thought... you've put more petrol in, increasing the weight of your car and decreasing the MPG. so maybe it's also factoring in the weight of the fuel remaining into the MPG calculation?