After completing a number of parachute dropping flights under supervision, the pilot refuelled the aircraft from drums using a hand pump which he understood delivered a specific volume of fuel per stroke. He then flew the aircraft on a short solo flight to drop parachutists from 3000 feet. On his return he was asked to conduct another flight ahead of an approaching rain storm. On reaching jump height the jump coordinator decided that the descent would be conducted to the north of the strip, away from the drop zone, due to the rain. As the parachutists descended, the aircraft was observed to fly to the north west of the strip and shortly after was obscured from view by heavy rain. The aircraft failed to return and was subsequently located by search aircraft approximately six kilometres to the west of the strip. It had impacted the ground in a right wing low attitude at slow speed. The investigation revealed that the fuel on board prior to the last take off was less than statutory reserve requirements. The engine had lost power due to fuel exhaustion. The fuel pump being used for the refuelling operation was found to be delivering less fuel per stroke than stated and the pilot had not use the dipstick to check the aircraft fuel quantity prior to the accident flight. The times being used by the pilot to determine fuel quantity required were taken from the aircraft tachometer. These times were substantially less than real time. It is considered that the pilot's decision to rely on a predetermined fuel quantity and allow himself to be rushed into departing ahead of a rain storm of unknown duration contributed to the development of this accident.