# Fuel gauge problem/diagnosis



## SPECSMAN (Oct 11, 2016)

On my morning journey to work.....

I usually refill the tank when the "miles remaining" is about 70-80 ...I was still at 190

Fuel gauge shows a solid 1/2

I always reset the odometer = it was at 286 miles, i.e. past my usual refuel

No fuel light

Drove as economically as possible to the next garage and put in* 54 litres!*

Question is, what is the probable fault?

I seem to recall that someone said if the gauge is wrong because of the dash pod; the "miles remaining" stays accurate, it isn't.

Is it the sender then? If so is it an easy fix?

Gauge shows full after refuel; was it "weighted" to 1/2?, it didn't budge in 20 miles.

Handbook says tank capacity is 62 litres, minus refuel 54 litres = 8 litres should/would that glow the fuel light?

Thanks in advance for any replies; all are welcome.

I will refuel at 200 miles as a precaution 'til its sorted.

Regards,

Specsman. [smiley=toff.gif]


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## Hoggy (May 8, 2002)

Hi, As fuel range & gauge were showing much the same, but incorrect amount, I would suspect sticking fuel level senders.
Filling the tank may have freed them up.
Hoggy.


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## SPECSMAN (Oct 11, 2016)

Hoggy said:


> Hi, As fuel range & gauge were showing much the same, but incorrect amount, I would suspect sticking fuel level senders.
> Filling the tank may have freed them up.
> Hoggy.


Thank you Hoggy; we can always rely on you!

You say senders, in plural; there is more than one?

Hopefully it/they have freed itself/themselves, as you say, I refuel 7-10 days, I will report the result here.

Specsman [smiley=toff.gif]


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## Hoggy (May 8, 2002)

Hi, Quattro TT has 2 level senders.
Hoggy


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## SPECSMAN (Oct 11, 2016)

Hoggy said:


> Hi, Quattro TT has 2 level senders.
> Hoggy


So...... assuming the fault does not go away, is it good practice to change both?

I have looked on eBay; one is just a sender and the other is combined with the pump?

Is there a "how to".

Thanks again Hoggy. Hope to return all these favours one day!

Specsman 8)


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## Hoggy (May 8, 2002)

Hi, The resistance of the level senders changed in May 2002, so ensure you get the correct ones.
Cleaning the resistance tracks with toothbrush & switch cleaner has worked in the past. 
Plenty of info, do a search.
Hoggy.


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## outdoor stevie (Nov 24, 2013)

Fuel pump with sender attached to it below the drivers side rear seat base make sure the fuel is very low when you go in, sender attached to the side of the pump which you will have to remove to get to the sender gizmo, there is a big rubber washer sealing ring around the hole and the pump which you may have to replace cos the old one may swell up when you go in so might be worthwhile getting one anyway TPS have them.

Stevie


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## SPECSMAN (Oct 11, 2016)

outdoor stevie said:


> Fuel pump with sender attached to it below the drivers side rear seat base make sure the fuel is very low when you go in, sender attached to the side of the pump which you will have to remove to get to the sender gizmo, there is a big rubber washer sealing ring around the hole and the pump which you may have to replace cos the old one may swell up when you go in so might be worthwhile getting one anyway TPS have them.
> 
> Stevie


Golden advice, thank you.

Specsman. 8)


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## Hoggy (May 8, 2002)

Hi, Primary pump is on the right, secondary pump on the left both have fuel level sender units.
Hoggy.


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## SPECSMAN (Oct 11, 2016)

Interesting development.

As I suggested I would, I have just continued to drive the car, re-fueling at 200 miles.

The gauge has never dipped below 1/2......until today.

I set out for work, gauge was 1/3 ...great, I thought, Hoggy was right, it has "freed" itself.

Unfortunately, the gauge continued to plummet, fuel light came on, I was then on the motorway so I stopped at the services and looked for leaks. There were none.

Decided to fill it up, to gauge the current level, and it took 32 litres, (about what it should have been).

Here is the question.

Is it still the sender or senders; or could it be the gauge/dashpod?

Thanks in anticipation,

Specsman. 8)


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## Hoggy (May 8, 2002)

Hi, Depends on what the fuel range showed after you put 32 litres in.
Hoggy.


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## SPECSMAN (Oct 11, 2016)

Thanks for the prompt response Hoggy!

After re-fuelling, the miles remaining was 60 and it dropped slightly on my remaining journey.

Gauge was still just above the red sector.

I was happy using it when full was full and half was empty; I don't like low readings and warning lights though!

Hope this help to diagnose; thanks mate.

Specsman


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## Hoggy (May 8, 2002)

Hi, Fuel range & gauge were both showing much the same but incorrect level as you had put 1/2 tank fuel in, so level senders are still the prob.
Hoggy


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## SPECSMAN (Oct 11, 2016)

That's good news Hoggy.

I would like to attempt a repair/cleaning the "tracks" on the old unit; is this feasible? or is new replacement the best option?

Thank you very much for your assistance; time is money and the generous nature of you and indeed many on this forum is incredible.

Specsman 8)


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## Hoggy (May 8, 2002)

SPECSMAN said:


> That's good news Hoggy.
> 
> I would like to attempt a repair/cleaning the "tracks" on the old unit; is this feasible? or is new replacement the best option?
> 
> ...


Hi, Switch cleaner & a toothbrush has been known to work, for how long I don't know.
Hoggy.


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## SPECSMAN (Oct 11, 2016)

Thanks Hoggy,

I will have a go and report my findings here.

Can't do it on a full tank.

My kindest regards,

Specsman [smiley=toff.gif]


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## outdoor stevie (Nov 24, 2013)

Many folk just go on the number of miles done before filling up so it's not desperate is it? Just arrive at your figure and fill up then. If you are going to fix then best done on a low tank as low as possible cos you don't want to spill Any petrol inside the car at all!! Space is restricted to the opening of the hatch into the Tank and if you have a method of removing the fuel then great as its not pleasant on skin or latex gloves, a few connectors on top so take a picture as you go, and be careful with the senders as its a floaty thing on the end of an arm which you have to fold out of the way in order to remove out and thro the hatch and it attaches to the back of the tank I'll see if I can find a picture ok

Stevie


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## outdoor stevie (Nov 24, 2013)

See if this helps eh!




























Should help give you an idea.

Stevie

Sent from my iPhone using Tapatalk


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## SPECSMAN (Oct 11, 2016)

Outdoor Stevie,

Thank you for that brilliant information.

I have continued to drive the car as you suggest, but when it happened, I was on the motorway, with the gauge steadily plummeting to empty, then a fuel light flashing and the gauge needle and miles remaining on absolute zero - it was a bit worrying, I thought that I had split a fuel pipe!

I have to reduce the fuel level (by driving) and I have ordered the pump removal tool off fleabay. (was going to fabricate one, but it's only ten quid!).

I will report my findings.

Regards,

Specsman 8)


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## SPECSMAN (Oct 11, 2016)

Can anyone answer this? I suspect Hoggy would know!

In anticipation of doing the job, I wondered.......

If I connect a pot (variable resistor), to the centre pins, will that replicate the effect of the electrical resistance presented by the senders?

Could doing this present a problem by turning on the ignition with the pump disconnected?

I just thought this was a interesting experiment; I am eager to do the job but have to drive the fuel away first.

Thanks,

Specsman 8)


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## outdoor stevie (Nov 24, 2013)

I don't know what advantage doing that connection thing would give you but don't think it would do any harm. I bought a wee gizmo for emptying the tank that works with a drill and a couple of bits of garden hose and it emptied the tank in a few minutes into some containers leaving me with a nice empty tank to play in so it was well worth it as doing stuff in any petrol at all is not pleasant, remember to have loads of rags and old towels handy if not emptying it!!

Stevie


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## SPECSMAN (Oct 11, 2016)

outdoor stevie said:


> I don't know what advantage doing that connection thing would give you but don't think it would do any harm. I bought a wee gizmo for emptying the tank that works with a drill and a couple of bits of garden hose and it emptied the tank in a few minutes into some containers leaving me with a nice empty tank to play in so it was well worth it as doing stuff in any petrol at all is not pleasant, remember to have loads of rags and old towels handy if not emptying it!!
> 
> Stevie


This connection thing is just an experiment; getting to know how it works and maybe learning a new diagnosis method(?)
Twiddling the potentiometer to make the gauge/fuel light operate; pure playtime!!

I am happy to run the tank empty by driving it; I am carrying 5 litres of fuel in a can, in case over do it; I'm not too comfortable using a drill driven pump (nice fat sparks from the brush motor), in a rich fuel/air vapour environment!

Thanks again for all the golden advice; I was going to get a Bentley manual, then I saw the price!

Kindest regards,

Specsman 8)


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## SPECSMAN (Oct 11, 2016)

YABBADABBADOOOOO!         

Yes it works!

Ran the tank really low; and started work... I opened the doors and tailgate to aid ventilation. The pump nut removal tool off ebay, worked brilliantly.

I think the problem was that the float/variable resistor on the pump had fell off!

I cleaned both resistor tracks anyway, reassembled it and everything seems to be working.

Thanks of course to Hoggy, but also to outdoor stevie; his manual fully described the removal of the float assemblies from the pump, because one of mine had fell off; I would have struggled to know how it all fitted together.

Incidentally, I didn't bother removing all of the gubbins, just the bit that mattered.

Turned the ignition on and the display read 50 miles remaning; filled the tank and the gauge went straight up to full; it has never gone quite all the way up during my ownership.

In summary; 100% fix for £15 (for the removal tool and switch cleaner)

Specsman. 8)  8) 8)


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## freeway-cola (May 17, 2021)

Hi, slight resurrection but having a similar issue.

Bought my 2001 TT last week, from a dealer, found out on fill up on the way home that the petrol and distance remaining show 0 always.

Dealer advised to get diag done, which shows fault code 00771 G short with ground

I then popped my multimeter on pins 2&3 and getting a reading of 258 ohms.

Just want to check before I crack open the fuel tank to see if my fuel pump is in one piece that I'm barking up the right tree?! Failing that it's back to the dealer for them to sort it. Thanks!
Multimeter reading:


http://imgur.com/sZvKzrr


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## Hoggy (May 8, 2002)

freeway-cola said:


> Hi, slight resurrection but having a similar issue.
> 
> Bought my 2001 TT last week, from a dealer, found out on fill up on the way home that the petrol and distance remaining show 0 always.
> 
> ...


Hi, Always best to start your own topic, rather than resurrect an old topic.
Is this a quattro or FWD TT. & what position were the floats in when resistance reading taken?
Hoggy.


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## freeway-cola (May 17, 2021)

Hoggy said:


> freeway-cola said:
> 
> 
> > Hi, slight resurrection but having a similar issue.
> ...


Hi Hoggy, quattro, I haven't taken off the ring that seals the fuel tank, I did give it a go but wasn't confident with the hammer/screw driver method considering buying an eBay tool. so I don't know what the floats are doing.


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## Hoggy (May 8, 2002)

freeway-cola said:


> Hi Hoggy, quattro, I haven't taken off the ring that seals the fuel tank, I did give it a go but wasn't confident with the hammer/screw driver method considering buying an eBay tool. so I don't know what the floats are doing.


Hi, There are 2 pumps & 2 floats in the Quattro tank & resistance are measured with floats in both full & MT positions.
Float 1 Full 147 Ohm. MT 29 Ohm
Float 2 Full 140 Ohm MT 27 Ohm

Hoggy.


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## freeway-cola (May 17, 2021)

Basically get inside, and take a look to see where the float is and measure after moving the float - thanks, I'll feed back once I manage to get the damn ring off!!


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## Stustt (Jul 3, 2020)

freeway-cola said:


> Basically get inside, and take a look to see where the float is and measure after moving the float - thanks, I'll feed back once I manage to get the damn ring off!!


Jumping the gun a bit, take car for a diagnostic check, could be the gauge cluster, will take two mins to run a test.
DON'T start stripping out fuel pump when it's probably fine.


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## Hoggy (May 8, 2002)

Hi, If fuel range & dash gauge indicate the same but incorrect level. IE they show MT but there is actually 1/2 a tank it's usually the level sensors in the tank.
Hoggy.


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## freeway-cola (May 17, 2021)

Update....

So stripped the fuel pump and tested the float arm and resistance and is all working as expected, high resistance when up, low when down ( 2001).

Testing the resistance of the cable that goes from the fuel level sensor to the dash, I'm getting a reading of 680 ohms - that doesn't sound right to me, as this is without the fuel sensor circuits in play too.

I've verified it's not the earth by also trying the main fuel pump earth on the connector too and it's the same reading, so definitely the purple fuel sensor cable at fault.

Before I rip the dash apart to check connections there, can anyone confirm what this should be please?!



http://imgur.com/BoQknTI


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