What was found
PNX - FLT 515 - BLOCK TURNBACK, ON RIGHT RUNUP, NR 1 ENGINE DIDN'T ACCELERATE. ALL INDICATIONS REMAINED IN IDLE. INDICATION WITH SLIGHTLY FLUCTUATING EPR NEEDLE. FELT ENGINE VIBRATING AND HEARD 'KNOCKING' NOISE. IMMEDIATELY BROUGHT THROTTLE BACK TO IDLE AND SHUTDOWN THE ENGINE. TROUBLESHOOTING FOUND DEFECTIVE FUEL CONTROL UNIT AT ENGINE RUNUP. REMOVED AND REPLACED FCU IAW DC-8 MM 73-20-0 AND 73-20-1. OPS CHECKED AND ENGINE TRIMMED NORMAL IAW MM 72-00-0. (M)