The airplane had been fueled to capacity then flown on multiple flights. At the last stop, 18 gallons of fuel was added to each wing tank, which gave 60 gallons total, the pilot said. As the pilot prepared to leave, the left fuel boost pump was discovered to be inoperative. The pilot told a mechanic that she tried to start the left engine by placing the left fuel selector on the left engine and the right fuel selector to crossfeed. Since the right boost pump is downstream, between the right engine and the fuel selector, it would not pressurize fuel to the left engine. The left boost pump was replaced and the pilot departed. Approaching the destination, the pilot reported a loss of engine power and crashed in an open field. The throttle quadrant was not set for an engine malfunction. No fuel was found in the left wing tank. The left fuel selector was in the left tank position and the right fuel selector was in the crossfeed position, so that both engines would have been fed from the left wing tank.