fuel level

This winter i have been building a fuel and battery watch display. so this topic is NOT about how great my display is 
But about he fuel sender in the fuel tank...
While calibrating my display this WE i noticed a strange behaviour: fuel sender does not go up above ca. 70 litres due to sender being mounted on the low end of the fuel tank. So whatever display you mount to have better reading of actual litres in the tank, above 70 it will be showing 70 litres or full 110 litres depending on your calibration. Anyway you can not achieve correct readings

I had similar problem.
If the sender is a model with an arm you can bend and/elongate the arm so that the float at the end of the arm reaches exactly from bottom to the top of the tank.
If the sender is of the sliding float type then probably there is some dirt on the slides obstructing the float reaching the top.
It is very easy to open the tank inspection hole and to examine the problem.

Another problem I had with one of the water tanks was that the float seemed to stuck at the uppermost position near the tank fitting always showing full even if the tank was empty. I solved the problem with a Teflon washer which did not allow the float to reach the top position but stopped 3-4 mm lower.

Hi all,

Thanks for the good advice. I'll try by bending the arm a little (as soon as my tank is a bit more empty) but i'm a bit sceptical: the tank is mounted not fully horizontal, and the place where the sensor is, is the lowest part. So this part of the tank fills completely before the higher upper part. This could explain the 30 litres above "full level" ... ultrasonic on the upper tank side could be a solution, but since thetank is under the bed of the aft cabine, not much free extra height is available...