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Fuel guage stuck on full!

scotsgent

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Location
Fort William, Scotland
Car
Accord 2010. ES GT
I picked up my latest car yesterday - a 2010 accord tourer 2.2 i-tdec.

All seems well apart from a couple of niggles, but this morning, I now notice a more problematic fault.

When I picked up the car, the fuel gauge read half-full and I topped up before setting off for a 3 hour trip back home.

I filled the tank to its capacity, only stopping when the garage pump auto shut-off operated.

It now seems that the gauge is stuck on full!

I also seem to think that the mileage left to run on the digital display is more or less the same figure as it was after the fill up.

So, given that the gauge works OK (that is to say it climbs when the ignition is switched on and drops when its switched off and that the digital system still thinks the tank is full), then it would seem to me that the signal from the tank is the problem - maybe a stuck float level?

Has anyone experienced this or maybe has some pointers as to how to problem-solve it?

Cheers, Terry
 
if the 8th gen is same as 7th gen, you're probably correct.

on the 7th gen the cover over the sender unit reachable from the boot

but before doing that, check for any codes with an OBD reader
 
OK - I've done a bit more digging on this problem. sadly, my electrical knowledge is poor but maybe someone with some electrical savvy might come up with a clue as to the problem from the info' below.

There are no fault codes with my OBD2 reader.

The gauge reads full whatever the actual level of fuel in the tank.

When the ignition is turned off the gauge drops to empty, when turned on, it always goes to full.

I removed the rear seat and had a look at the connections to the pump/ sender. There are 4 wires going to the connector. A red and black (which I think is power and negative for the pump?). There are also a purple and orange wires going to the two other pins. I think (?) that these are power and signal to/from the sender. I checked the voltage of the purple wire and it was 11 volts.

I did some research and apparently the accord ohms value in the signal wire should be 4/5 ohms when full and 105 ohms when empty.

I measured across the two terminals with my meter and I think I am getting 20.5 ohms which would be around three quarters of a tank.

I went to the garage and put in another tenner, the ohms measurement of 20.5 didn't change (but am actually unsure if measuring the resistance between these two pins is the correct technique to get the proper value)?

I attempted to remove the inspection hatch into the tank to access and bench test the sender, but bottled out when even an extended breaker bar on a strap filter wrench wouldn't budge it and I feared I might break something!.

I have a couple of questions?

is there anything in the above which gives a clue?

If I had an open circuit (broken signal wire or loose connection at the gauge, would the effect be to send the gauge to the full position?

has anyone ever removed the instrument cluster - I would like to check for a loose connection at the gauge.

Any help at all or ideas for further testing anything would be gratefully received.

Cheers, Terry
 
no OBD codes makes it difficult to diagnose further

If you bought the car from a dealer then if I were you, next step is to take it back to them, they should fix it free-of-charge under sale-of-goods act (and don't tell them you've been poking around with a meter or screw drivers at the sender unit)


edit: oh dear, I've seen in the "newbie" section that it was a private sale, in which case "caveat emptor"

I only have info on the 7th gen Accords, if you intend to start doing a lot of DIY on this Accord you need to get a Honda workshop e-manual (DVD) for the 8th gen diesel.

On the 7th gen diesel, there is no electric pump in the tank, but I think there is on the 8th gen diesel, in which case you're correct about the wires i.e. 2 for the electric pump, 2 for the sender unit.

One basic rule of thumb, do not measure resistances of anything when it is in-circuit.

***uming that you are correct about the purple and orange wires, you measure the resistance across the socket with the purple/orange wires unplugged (the "sender" is not powered, it's a resistance). Indeed, if there are 2 separate plugs, one on the purple/orange and one on the red/black, just unplug the purple/orange and see what happens on the gauge on the dash.
 
Thanks for your input Brian, its much appreciated.

I had an idea in my sleep last night! :)

If I go to Maplins and buy one of these little resistors, say rated at 40 ohms. This rating should be about half-way between the empty and full ohm readings and which a 'good' sender would signal if the tank was approximately half full.

I could unplug the connector from the tank end and bridge the two sender wires (purple power and orange signal) with the resistor. This would then mimic a sender in the half-full position.

I would then switch on the ignition, if the gauge needle reacted appropriately, then the problem must lie in the sender unit. If no change, then the problem would probably lie in the signal wire or gauge?

Is this idea sound?

I will look for a workshop manual CD. On first glance, most of the ones I could see were of the USA petrol versions, I suppose EU manuals exist somewhere?

Cheers, Terry
 
Hi Terry, what you describe is a good idea providing that the purple and orange are the correct wires.

You said that you measured 11 volts on the purple wire, before disconnecting anything, check the voltages of all the colours (from chassis). Be careful with the probes btw, make sure the probe you use does not touch/bridge to anything else while measuring voltages.

I would expect that red = 12V, black = 0V, and if purple = 11V then orange may be a similar voltage (it depends on the way the circuit works).
Then if possible, re-check the voltage on each colour with them disconnected.

Re the manual, you won't find a Haynes manual for the European Accord, in the US the equivalent car is the Acura TSX, the US Accord is very different.

cheers, Brian
 
OK Brian,

I'll try and get hold of a resistor or two this week,

I'll also run the checks on the wiring you suggest.

I discovered how to run the 'self-diagnostic' test on the gauges which the 8th gen' possesses. All the gauges operated as they should during the test, including the fuel gauge and no faults were found. So, if this self-diagnostic test is of any value then it seems to saying that my gauge is OK?

In the end, the fact that this problem occurred at the instant of filling up the fuel tank seems to me to logically point to a mechanical/electric issue with the sender, but we shall see. A short or open wire problem occurring at the same time as I filled up seems unlikely really?)
_____________________________________________________________________________________________________

Actually my Accord is a pretty fine example I think, more or less mint but with a few wee issues I am sorting through: rear washer and low pressure at the front washer now sorted (Algae in the bottle and pipes) and handbrake adjustment now sorted.

I now have two outstanding issues - the fuel gauge (which I will get to the bottom of, I hope) and a jammed fuel filter cap.

The fuel filter cap might be a problem. I have bought a Chinese removal tool but the cap has been damaged by a previous attempt to remove it (with an oil filter chain tool I think) and the chinese tool slips when the pressure is applied.

I will get into this issue when I have sorted the fuel gauge!

Luckily, I have a fishing pal who owns a garage and although I don't wish to use him too often, if push comes to shove I can always take the car to him for anything outside my abilities.

I much prefer to do my own stuff as much as I can - nothing better for gaining knowledge and keeping the brain ticking over!

Cheers, Terry
 
I haven't mad too much progress on this issue - I've been side tracked with other things.

However, this is now the only issue standing in the way of perfection! So, I intend to get to the bottom of things.

I did remove the sender but only then to discover that the battery on my multi-meter was faulty and so I got spurious readings - I will probably retry with this in a day or two.

There is one thing though? My battery is fully charged at 12.6 volts but measuring the power into the sender unit gives me 11.24 volts.

Is this voltage drop significant? Would this effect the readings coming out of the sender ?

Anyone know?

Thanks, Terry
 
scotsgent said:
I haven't mad too much progress on this issue - I've been side tracked with other things.

However, this is now the only issue standing in the way of perfection! So, I intend to get to the bottom of things.

I did remove the sender but only then to discover that the battery on my multi-meter was faulty and so I got spurious readings - I will probably retry with this in a day or two.

There is one thing though? My battery is fully charged at 12.6 volts but measuring the power into the sender unit gives me 11.24 volts.

Is this voltage drop significant? Would this effect the readings coming out of the sender ?

Anyone know?

Thanks, Terry
Hi Terry

An electronic circuit does not have to work the way you're thinking. There are many variations of electronic circuits, and measuring voltages at either end of a variable resistance (which a sender unit is), with the variable resistance in-circuit, will tell you nothing unless you have the circuit diagram of the amplifier that the variable resistance attaches to. Or with a test manual that says what the voltages should be.

The best thing is to measure the resistance of the sender unit with the sender unit completely disconnected, and go from there.

cheers, Brian
 
Hi Brian,

Thanks for the link to the fuel pump. My pump, of course is OK - its just the fuel sender I may need.

My question regarding the voltage drop at the purple power wire was because I found a USA service item on checking the sender unit.

The first part of the process was to check for battery voltage at this power wire. "If the voltage is not satisfactory then check for a short or open in the power wire or the sender wire".

The problem here is that it does not give an idea as to what might be satisfactory or not and so I was trying to ascertain if a reading of 11.3 as opposed to 12.6v at the battery indicated an 'unsatisfactory' reading.

I would also like to find out the ohms value range for a satisfactory fuel sender. Again, I do have some USA info' for the 2009 Accord, but I am aware that it is a different, bigger machine than the UK version. The range for the USA model is around 20 ohms FULL and 780 ohms empty. Other sources have given older Hondas as 20/120?

I called Holdcroft Honda and asked for data from their parts manual but they say they have no info' and when I asked how a technician would check the resistance of a sender if they don't have the values, they replied " they would just use their computer"!

I can remove the sender again and again check the ranges from full to empty on my particular unit, but ideally I would like to have the 'correct range' to properly compare before I pull it out. One of the reasons is that pulling out the pump and sender is a bit fiddly and each time I do it, I risk damaging the float arm or needing a new gasket (which Honda only sell as part of a 'set' for £90!)

So, I wonder, does anyone out there have the data: That is what is the proper resistance range on a good fuel sender for a 2009 Honda Accord I-tdec Tourer?

I guess this info' might be contained in a UK service manual for this vehicle?

Cheers, Terry
 
The "USA service item" may not be the same car or engine, indeed even if it was similar, It also depends which two points being used to measure volts.

Re asking a dealer, a dealer isn't going to want to give out technical info like this unless you offer some financial incentive LOL

Re the ohms values, it will be on a Honda e-manual (DVD), it might be worth getting a copy.
 
there is a fuel sener mentioned above for 70quid, seems like a good idea rather than faffing about with things and relying on articles from entirely different vehicles.

there is a 14 day return also so a bit of a no brainer, if it doesnt work return it.
 
Hi scotsgent, just wondering if you got your guage problem sorted. I bought a 2008 ex i-dtec saloon last week privately. It had half a tank of fuel when I got it. I filled up at the weekend and have since done 120 miles and the guage is still showing full. Looks like the exact same problem you had. Any help would be greatly appreciated.
Dale
 
Dto80 said:
Hi scotsgent, just wondering if you got your guage problem sorted. I bought a 2008 ex i-dtec saloon last week privately. It had half a tank of fuel when I got it. I filled up at the weekend and have since done 120 miles and the guage is still showing full. Looks like the exact same problem you had. Any help would be greatly appreciated.
Dale
I had the same problem I was thinking it was stuck on full but it starts dropping after 150 miles always after the top up.
 
Seahawk said:
I had the same problem I was thinking it was stuck on full but it starts dropping after 150 miles always after the top up.
Thanks for that seahawk. I will go for a good run the weekend and see if it starts dropping.
 
My 8th Gen Accord needs to do about 120-150 before the needle moves from full to just a bit lower, maybe a needle width, my old 4th gen was the same. When near half full drops like a stone to empty. But good for about 600 miles on a tank full not really measured it.
 
Thanks for the replies guys, the guage has started to go down now so panic over. I did notice the half tank I had when I got the car went down quick.
 
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