C.  Remove igniter plugs from combustion chamber outer case. If required for reference, identify location (left or right) from which the plugs were removed.
CAUTION:  TO AVOID POSSIBILITY OF THE DISENGAGEMENT OF THE SOCKET FROM THE WRENCH EXTENSION DURING REMOVAL OF THE IGNITER PLUGS (WHICH COULD RESULT IN THE LOSS OF THE SOCKET BETWEEN THE FAN DUCT AND THE OUTER CASE) PERMANENTLY SECURE THE SOCKET TO THE EXTENSION BEFORE USING.
D.  Individually wrap igniter plugs in wax paper and place in a suitable box.
4.  Install Igniter Plugs
A.  Check condition of igniter plug boss threads . Clean threads using Pratt and Whitney Aircraft P/N 33647 (formerly P/N 8597) tap if necessary.
B.  Remove the protective covers from the igniter plugs. Clean the threads of the igniter plugs and combustion chamber case bosses with cleaning solvent. Apply a small quantity of antigalling or antiseize compound to the threads of the igniter plugs, case bosses and gasket faces.
CAUTION:  DO NOT USE ANTISEIZE COMPOUND (SILVER GOOP) ON THE IGNITER OR BOSS THREADS IF A DIFFERENT COMPOUND WAS USED BEFORE. IF SILVER GOOP IS USED WHERE OTHER COMPOUNDS HAVE BEEN USED BEFORE, IT CAN BECOME HARD AFTER ENGINE OPERATION.
CAUTION:  MAKE CERTAIN THAT SAME TYPE IGNITER PLUG IS INSTALLED AS WAS REMOVED. USE TWO GASKETS (PRATT AND WHITNEY AIRCRAFT, P/N 182888 OR 266315) WITH SHORT TYPE IGNITER PLUGS ONLY (REF P/N 464332). THE ABOVE LISTED IGNITER PLUGS MUST BE USED ONLY ON ENGINES INCORPORATING THE FOLLOWING CONFIGURATION OF PARTS.
(a)  
COMBUSTION CHAMBER OUTER CASE P/N 490547.

(b)  
ONE-PIECE DESIGN COMBUSTION CHAMBERS OF P/N 534XXX SERIES.

C.  Before installing igniter plugs look through igniter plug bosses on combustion section fan duct at each igniter plug guide to be sure that guide is centrally located. If required, insert suitable tool through plug port and align guide to its approximate proper position.
NOTE: Locally fabricated tool may be used (Fig. 402).
D.  Install new washer on each igniter plug and insert plugs through holes in fan duct igniter bosses and into mating threaded holes in combustion chamber outer case. Prevent excessive galling of igniter plug tip and lower shell by bottoming each plug by hand before torquing. This will ensure that igniter plug and burner can igniter plug swivel are properly aligned. See Fig. 401 for the necessary radial distance for a correctly installed igniter plug.
500 
Feb 20/91  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  74-21-21 Page 403 

E.  Tighten plugs to 300-360 pound-inches.
CAUTION:  PERMANENTLY SECURE SOCKET TO EXTENSION BEFORE USING TO AVOID LOSS OF SOCKET BETWEEN FAN DUCT AND OUTER CASE.
F.  Install a new packing on each holder and position holders on respective right and left fan duct igniter plug bosses. Position a spacer sleeve on each of four bolts. Insert these bolts through holes in holder and boss, position washers on bolts, and secure with self-locking nuts. Tighten bolts.
G.  Remove protective caps and install a new packing in groove on OD of igniter plug coupling nuts on left and right output cable assemblies. Clean threads on ID of these nuts with a petroleum solvent and apply Molykote Type Z. Carefully insert lead into terminal well of igniter plug and thread coupling nut on plug. Tighten nut 140-160 pound-inches.
CAUTION:  INSUFFICIENT TORQUE ON LEAD NUTS CAN CAUSE IGNITION RADIATED NOISE WHICH CAN BE PICKED UP BY AIRCRAFT RADIO EQUIPMENT.
H.  Perform ignition system (audible) check (Ref 74-00 A/T).
500 
74-21-21 Page 404  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Feb 20/91 

IGNITER PLUGS - REMOVAL/INSTALLATION
PWA 74-22-1, Page 404, Sep 01-90
G42786

500  Igniter Plug Removal/Installation 
Feb 20/91  Figure 401 (Sheet 2)  74-21-21 
Page 405 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

Combustion Chamber Igniter Plug  500 
74-21-21  Guide Aligning Tool  Feb 15/81 
Page 406  Figure 402 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

ENGINE IGNITION CONTROL - DESCRIPTION AND OPERATION
1. General
A.  The ignition system for each engine is energized through a start switch and start lever actuated switches. The start levers are located on the control stand (Fig. 1). The start lever actuated switches are below the control stand. The start switches are located on the forward overhead panel (Fig. 2). When the ignition system is energized the ignition exciter produces a high voltage pulsating current to the igniter plugs. The spark produced between the igniter plug electrodes vaporizes fuel droplets. The fuel-air mixture is brought to the proper temperature that is required for ignition.
　
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