Distance to empty calculation

[immortality]

Hey guys,

Got a curly one...... The distance to empty calculation on the missus VX Calais is wrong.

As far as I know it has a 75 litre tank (standard VX size going by the owners manual), fuel used sort of roughly matches what goes in at the pump (within 1 litre) however like clock work every time when you have used just over 50 litres it chimes the fuel low warning and the distance to empty is low (manual says this happens with about 8 litres remaining I think). It all seems to suggest the calculation is based on a 60 litre tank? However when I go into the settings after filling it up it does show about 75 litres in the tank.

It's got me stumped.

I did read somewhere that the models fitted with LPG only had a 60 litre tank so I'm guessing that maybe the cluster has been set wrong?

Anybody know how to check/fix this?

Thanks

[Jayme]

nah it gives me the shits too.... I think you have come across the bane of vt > vz owners lol. officially they hold 75 liters from dead empty to full, but in practice the senders read zero with at least 15 liters still in the tank or something like it.

ive reprogrammed my dash (vy but still similar) with the correct (ish) ohms > liters table by filling up in 5 liter increments and reading out the sender ohms from the dash in engineering mode. I assume full is 75 liters and work backwards down the table from there. the bottom end of the table is still a fudge factor because if you fill it up at the at "dead empty" when the sender reads nothing its still only like 55 liters at the pump.. im tempted to reprogram the dash to tell it that FULL is the actual usable capacity of the tank which is about 60 liters. then all the distance to empty calculations should become correct.


for yours, as a start... if you coudl be bothered... drain it till its dead empty then go into engineering mode and read out the fuel sender ohms. start putting fuel in and note when the ohms starts going up. that will tell you how close your sender is to actual empty.

[immortality]

I'm tempted to put a 5 litre fuel container in the boot and then drive it till it runs out of gas to work out the true usable fuel capacity.

It is annoying though because the analogue fuel gauge is still showing a little more than an 1/8th of a tank of fuel which seems to be fairly accurate yet trip comp is telling me to fill the bloody thing up.

Yeah, I'm taking about 55-56 litres at the pump and generally the trip comp is showing about 50-60 km to empty at that stage.

It's annoying, I want to take it on a long trip and in theory I should get there easily on a single tank of gas however with how it's currently programmed it's going to beep at me before I get there

[immortality]

OK, this is really getting to me now.

How do I gain access engineering mode in the cluster so that I can check the calibration?

Thanks

edit: I'm thinking that the only true solution might be to remover the fuel sender unit and bend the arm slightly to get a true empty reading but this seems a bit drastic and a PITA. Can you access the fuel sender unit without dropping the fuel tank?

[antus]

You wont need to drive it 'till empty. You can disconnect the fuel hose up somewhere up stream from the pump and set up a hose to fill a bucket, power up the pump and run it 'till its sucking air. then do your measurements and poor the fuel back in without moving the car.

[bldnut]

the fuel low and distance till empty calc in the dash comes on when you have a certain range left it isn't calculated on just 8L of fuel left, if your light is coming on at 1/8 of a tank I will take a stab in the dark and say your average fuel usage on the dash will show around 17-25L/100k and when you fill the car the dash only shows 300-450k till empty, if you fill the car up and reset the fuel usage and trip meter then take the car out on the highway for 1/2 hour you should see the distance till empty increase up to around 750k till empty, and on a drive like that your low fuel light will come on when the needle is in the red and you would have around 8L of fuel left.

[yoda69]

bldnut is correct, low fuel light is set to come on when distance to empty is about 80km based on your fuel consumption over the previous 5-10 litres.
Most of the problems came about due to something in the fuel (sulphur I think) contaminating the sender and upsetting the resistance, the sender contacts are actually immersed in the fuel.
It was around VX where they changed the sender to work in the opposite direction and have high resistance when empty instead of high resistance when full.
Pre change if the sender was contaminated would get high resistance and the fuel tank would show you still had 1/4 to a 1/2 tank when you ran out, there were plenty of customer complaints over this.
Post change if the sender was contaminated you would get high resistance and the vehicle would show empty when there was still 20 Litres left in the tank, which sounds like what yours is doing.
All it would take is one tank of bad fuel and you're senders stuffed. I think fuel quality today has improved in this respect so less likely to happen these days, but could have very easily happened when the vehicle was new.
Best bet is to replace the sender, second to that bend the arm.

[immortality]

Thanks for the replies guys.

Average fuel consumption is showing about 13L/100km. Distance to empty is generally about 500km when filled. Fuel used is generally fairly close to what is put in and total fuel in the tank is showing about 75 litres when filled. Car is used for plenty of stop/start as well as short trips on the motorways but never really any long trips. I have checked fuel usage and distance calibrations and they are fairly close to where they should be.

If I reset the trip comp when filling the tank the average returns to about 13/100 by the time the tank is empty.

I could possibly confirm the contact issue by double checking what readings the dash is seeing with a full and (supposedly) empty fuel tank. I'm just not sure how to get into the engineering mode to get this data.

[monaro308]

Is this what you want?

single window.png

[slewinson]

According to Lord Google, holding mode and up while starting engine should do it.

Simon