in the elektor 07-08 of this year,
you will find a microlight fuel gauge circuit from jean pierre duval (sound french cocorico).
this could be a good start.
the line below is from the article.
"This is an FHKSC 932-8501 from Digmesa  & . This detector can meas-ure fluid flows from 0.03 to 2.0 l/min, equiv-alent to a range of 1.8 to 120 l/hr "
here is the link for the datasheet: www.digmesa.com/digmesa/upload/pdf/FHKSC/ 932-850xxxx_GB.pdf