The pic had been airborne in the lcl area to let parachute jumpers jump fm his acft. To lose alt quickly the pic performed a prolonged slip. On the final app the eng quit and alt was insufficient to reach the rwy for lndg. The off arpt lndg was unsuccessful. The pic stated that the poss cause of the acc was improper fuel flow resulting fm the slip and the abbormal attitude associated with it. It was also imcumbant upon the pic for a safe lndg to have selected the proper fuel posn by referring to the owner’s manual. The owner’s manual cautions abt proper fuel selector positioning. Fuel selector on ‘both’ is required for all but straight and level flt. The fuel selector was found posnd to ‘off’ during insp of the acft and 10 gal of fuel was found in the rt tank. No fuel was found in the left tank.