What was found
NR 1 AFT FUEL PUMP LIGHT ILLUMINATED DURING PREFLIGHT. 30K FUEL ON BOARD. GROUNDED-YES. PERFORMED B737-900 FIM 28-22 TASK 803, GVI OF CONNECTOR D70, PINS AND PUMP CONNECTOR APPEARED OK. PERFORMED PUMP INSULATION RESISTANCE TEST, REF B737-900 AMM 28-22-00, GOOD. W/ C/B CLOSED AND COLLAR REMOVED, 115VAC AT ALL 3 PINS. INSTALLED D70 AND PUMP OPERATIONS NORMAL UNTIL SHAKEDOWN MOVEMENT OF WIRES AT THE CONN D79 WHILE PUMP ON CAUSED A SPARK TO EXIT THE BACK OF THE CONNECTOR. PUMP STOPPED AND GFI TRIPPED. REMOVED AND REPLACED NR 1 AFT FUEL PUMP PLUG D70, REF B737-900 WDM 28-23-11 AND SWPM 20-61. PERFORMED OPERATIONS TEST OF GFI R18, IAW AMM 28-22-41-720-802. CHECKS GOOD. PERFORMED BONDING CHECK OF NEW PUMP, REF 28-22-41-400-801. REPLACED NR 1 AFT BOOST PUMP, REF AMM 25-22-41. GROUND VERIFICATION GOOD.