What was found
ENGINE #1 START STALLED BRIEFLY @ 20% N2, THEN RECOVERED TO START NORMALLY. FA IN BACK HEARD 3 BANGS. GROUNDED - YES. PERFORMED B737-800 FIM 80-05 TASK 806, NO FAULTS NOTED OR DEFECTS. SUSPECT PACK, R/H, BEING ON DURING START ATTEMPT AS CAUSE FOR SLOW START. PERFORMED BOTH ENGINE START WITH FLIGHT CREW, ALL OPS NORMAL.