TM 9-2320-211-20
Section XVI. IGNITION SYSTEM--GASOLINE ENGINE
2-119. General
screws (1, fig. 2-144) holding the distributor to the
T h e ignition system is composed of an ignition
top of the distributor drive housing, until the
w i t c h , c o i l , d i s t r i b u t o r assembly, spark plugs,
pointer and the five-degree notch coincide.
spark plug wires, and primary wire. The ignition
NOTE
system produces and delivers high voltage current
Turning the distributor body clockwise will
to the spark plugs.
a d v a n c e the spark, a n d counterclockwise
2-120. Ignition Timing
will retard the spark.
a. G e n e r a l . T h e p r o c e d u r e f o r c h e c k i n g a n d
NOTE
correcting ignition timing for engines with a sealed
It is not necessary to disconnect the
ignition system requires special adapters (fig. 2-
distributor vent line, since the line will flex
142) which are part of the electrical connector tool
sufficiently to allow close adjustment.
kit.
(11) Tighten the distributor clamp screws
when the timing is adjusted properly.
(12) Disconnect the timing light and remove
the timing testing adapters from the spark plug and
the regulator.
(13) Connect the No. 1 spark plug cable.
Connect the battery harness to the generator
regulator.
b. Checking and Correcting Timing.
(1) Clean, adjust, or replace the distributor
p o i n t s as necessary (para 2-122d).
(2) Remove the spark plug cable from the No.
1 spark plug; unscrew the coupling nut and screw
on the spark plug testing adapter.
(3) Place the spark plug cable on top of the
spark plug testing adapter.
(4) Fasten the clip of the red lead from the
2-121. S p a r k P l u g s
timing light to the terminal on the side of the spark
a. Removal.
plug adapter.
( 1 ) Loosen the nut securing the spark plug
(5) Disconnect the battery harness at the
the cable from the
c a b l e t o t h e p l u g . Disconnect
generator regulator, and install the regulator testing
plug.
adapter.
( 2 ) Unscrew and remove the plug from the
(6) Connect the harness to the adapter. Turn
recess in the cylinder head. Discard the spark plug
the voltage selector switch of the timing light to 24
gasket.
volts.
( 3 ) Repeat Steps (1) and (2) above for the
(7) Connect the red gloved lead to either
r e m a i n i n g : spark plugs to be removed.
terminal on the adapter and the black gloved lead
b. Cleaning and Inspection.
to a suitable ground.
(1) Clean the spark plugs with standard plug
( 8 ) Apply chalk to the 5-degree BTC mark
cleaning equipment.
(2) If the electrodes are excessively burned or
observation.
worn, replace the plug or plugs as required.
(9) With the engine running at idling speed
c. Adjustment.
(450 rpm), direct the beam of light down at the
(1) Use a round feeler gage to check the gap
t i m i n g pointer on the timing gear cover. If the
between electrodes. The gap should be 0.030 inch.
timing mark is alined with the pointer when viewed
(2) If necessary, adjust the gap by bending the
with the timing light, the timing is correct.
side electrode.
