The pilot ordered 42 gallons of fuel to be added to the aircraft which would bring the total fuel load to 60 gallons. The lineman added 4.2 gallons bringing the total fuel load to 22.2 gallons. The pilot did not verify the fuel load prior to departure. The aircraft was flown from San Juan to Vieques in which 12 gallons were burned. No fuel was added and the pilot again did not verify his fuel load. The flight departed Vieques en route back to San Juan with 10.2 gallons of fuel. On descent into San Juan both engines failed and a forced landing was made in a sugar cane field. After rolling about 100 yards the left landing gear collapsed. Post crash examination of the aircraft revealed it contained 36 ounces of fuel with no evidence of leakage. The engines were operated to full power with no evidence of mechanical failure or malfunction after the accident. The lineman had been hired as a part-time employee on 1/2/89. He stated he was working only his fifth day and that he had no formal refueling training.