What was found
FLT#2220, LHR-JFK. (ETOPS) 'ENG 1 FIRE LOOP A INOP ( ENGINE FIRE DETECTION SYSTEMS 1) LOOP A ); T/S CFDS PREVIOUS LEGS- DID NOT RECORDED ANY FAULTS. AVATAR REPORTED FAULT RECORDED AT PHASE 2- ENGINE START - WHEN FAULT PLACED ON DEFERRAL RESISTANCE ACROSS PINS J/K OF 210DIA MEASURED 1490 OHMS INSULATION CHECK FOR 2WDIA PIN J AND K TO DND MEASURED 10G OHMS FOR BOTH. PERFORMED A GVI FOR ALL THREE DETECTORS - NO DEFECTS NOTED. RAN ENG BEFORE REPLACING FDU FAULT DID NOT APPEAR- REMOVED AND REPLACED 210D1 PRECAUTIONARY REFER AMM 26-12-34-WITH ENG RUN FAULT DID NOT APPEAR- FAULTS CLEARED MDDR 57913 MX4 UPDATED PLACARD REMOVED M/C ADVISED.'