fuel tank display is wrong

[ultranaut]

Filled the tank and started driving, few minutes later I realise the display says the tank is only 3/8ths full. Check the miles remaining and it says 130. Drive an hour and the tank display says I only have 1/4th a tank remaining. Stop the car and turn it back on, the display goes right back up to 3/8ths full.

Anyone have any idea what's up?

 

[Polak]

You were on a hill.

 

[740GLE]

filling up while running the engine will kinda freak out the cluster/gauge. Also filling up partially, driving around then topping off a few min later will also freak out the gauge.

I filled with a $30 prepaid debit rebate card, I then let the person behind me fill up as I didn't want to be a pain and fill up again. I drove around the block and came back to brim the tank. Once it was brimmed, my gauge displayed 3/4 to 7/8's full. I drove home 50 miles, and by the time I made it home the gauge was normal full.

 

[MayorDJQ]

filling up while running the engine will kinda freak out the cluster/gauge. Also filling up partially, driving around then topping off a few min later will also freak out the gauge.

I filled with a $30 prepaid debit rebate card, I then let the person behind me fill up as I didn't want to be a pain and fill up again. I drove around the block and came back to brim the tank. Once it was brimmed, my gauge displayed 3/4 to 7/8's full. I drove home 50 miles, and by the time I made it home the gauge was normal full.

I've done partial fills and for one reason or another finished the fill elsewhere on several occasions. I've never had an issue with the gauge.

The only time I've gotten an "unusual" display was the first time I filled my '09. I filled it at "full blast" and upon driving away only had 7/8 of a tank. Every fill since then I've filled at 1/2 blast or less until the nozzle kicked off, then trickle filled to the brim. This method yields a FULL reading each time.

3/8 of a tank would indicate to me that there might be a problem with the sender.

 

[dweisel]

Filled the tank and started driving, few minutes later I realise the display says the tank is only 3/8ths full. Check the miles remaining and it says 130. Drive an hour and the tank display says I only have 1/4th a tank remaining. Stop the car and turn it back on, the display goes right back up to 3/8ths full.

Anyone have any idea what's up?

How many gallons did you put in while fueling? What was the fuel tank reading before you filled?

 

[ksing44]

filling up while running the engine will kinda freak out the cluster/gauge.

Mine acted weird by just turning on the key while filling. The tank didn't show properly for a couple of days, about a half dozen cycles of running the car and shutting it down. Now I never fill the car with the key in the on position. It never happened again. I should add that I am not alone in having this experience, even though others commented that it doesn't happen to them.

 

[MayorDJQ]

Mine acted weird by just turning on the key while filling. The tank didn't show properly for a couple of days, about a half dozen cycles of running the car and shutting it down. Now I never fill the car with the key in the on position. It never happened again. I should add that I am not alone in having this experience, even though others commented that it doesn't happen to them.

Do you have VCDS? I wonder if you can reset the display/sender when it's giving a weird signal.

 

[dpg]

I've had weird fuel gauge levels while filling up with the key on with previous cars, but it would correct itself with turning the car off for a few seconds and starting it back up fixed it. Haven't tried or done it with the TDI

 

[ksing44]

Do you have VCDS? I wonder if you can reset the display/sender when it's giving a weird signal.

It only happened once for me, so I didn't do anything special. The one time it did happen, it finally corrected itself after a few cycles of driving. Perhaps if I had checked with VCDS I could have done something, but it fixed itself and never happened again because I don't turn the key on anymore.

 

[ultranaut]

Whatever went wrong was fine the next time I filled up. I've put two tanks through it since then without issue. Thinking back on this incident, the only slightly unusual thing about this fuel up was that I didn't top off the tank. I don't always top off but most of the time I do. I've had some other quirky things with the fuel displays in the past, namely the estimated miles per tank counting down much faster than normal (e.g. it says 100 miles remaining, I drive 60 miles with above average mpg and yet the estimate has dropped down to only 10 miles remaining). I suspect that one was caused by a software upgrade during routine service because it started happening shortly after one about a year or so ago. They've upgraded it again since then and that seems to have made it better but it still occasionally doesn't seem to be quite as accurate as it used to be.