What was found
FIRE WARNING ON NR 4 ENGINE. SECURED ENGINE AND DISCHARGED FIRE BOTTLE. MASTER FIRE WARNING CAME ON MOMENTARILY WITH NO LIGHT IN ANY LEVER OR ON FLIGHT ENGINEER PANEL. TESTED EACH ENGINE FIRE WARNING SYSTEM, NR 4 ENGINE WOULD NOT TEST. MASTER WARNING FLASHED ON AND OFF. AFTER ENGINE WAS SECURED FIRE WARNING TESTED OK. FOUND BROKEN PIN IN NR 4 LOWER LOOP CONNECTOR. REPLACED LOWER LOOP. FIRE WARNING TESTED GOOD.