What was found
FUEL QTY LT MAIN FLUCTUATES BY MAX OF 700 FMC FUEL PREDICTIONS OF BELOW EXPECTED QTY'S. ACFT GROUNDED. ACCOMPLISHED FUEL TRANSFER FROM CENTER TACK TO LT WING REF MM 28-26-00-650-802. TRANSFERRED FROM LT WING TO CENTER TANK. NO FAULTS NOTED. VERY STEADY READINGS. PERFORMED RESISTANCE READINGS AND PLUG INSPECTION, ALL PINS ARE SEATED CORRECTLY. NO FAULTS FOUND. REMOVED AND INSTALLED NEW FQIS UNIT REF 28-41-81/401. PERFORMED SYS OPS TEST REF 28-41-00-710-801. SYS CKS NORMAL. FQIS GROUND TEST PASSED. NO FAULTS WERE PREVIOUSLY LOGGED AND NO FAULT HISTORY LOGGED.