Rockwell Commander 112 - Ignition Harness

ROCKWELL
COMMANDER
112/B/TC/TCA
MAINTENANCE MANUAL
SECTION IV
POWER PLANT
AND PROPELLER
ing flange to a point where the light comes on, then
slowly
turn it in the opposite direction until the light
goes
out. Bring the magneto back slowly until the light
just comes on. Repeat this procedure with the second
magneto.
NO"I
AC timing lights operate in the reverse
manner as described above, the light
goes out when the breaker points open.
After both magnetos have been timed, check to ascer-
tain that both magnetos are set to fire together. Back-
off the crankshaft a few degrees, the timing lights
should go out. Bring the crankshaft slowly back in
direction of normal rotation until the timing marks
are in alignment. At this point, both lights should go
on simultaneously.
MODELS 112TC/TCA. INSTALLATION AND TIMING.
The magneto
must be installed with its timing marks
correctly aligned. Rotate the crankshaft in direction
of normal rotation until number one cylinder is on the
compression stroke and approximately 20 degrees be-
fore top dead center (BTC).
I WARNING I
The magneto is grounded through the
ignition
switch, therefore, any time
the primary (switch) lead is discon-
nected, the magneto is in a switch ON
or hot condition. Before turning the
propeller by hand, remove high tension
cable outlet plate from magneto or dis-
connect all spark plug cables to prevent
starting engine accidently.
Clamp an ignition timing pointer on the advance timing
mark on the rear of the starter ring gear. The starter
ring gear may be marked at 20 and 25 degrees. Con-
sult engine nameplate for correct advance timing mark
to use. Continue rotating the crankshaft until the tim-
ing pointer and the parting flange of the crankcase
align. Leave the crankshaft in this position until the
magneto is installed. In the event that an ignition
timing pointer is not available an alternate method
may
be used. Rotate the crankshaft in directioJ'l of f
normal rotation until number one cylinder is on the
compression stroke and continue rotating the crank-
shaft until the correct advance timing mark on the
rear of the starter ring gear is in exact alignment
with
the small drilled hole located at the two 0' clock
position on the front face of the starter housing.
Leave the
crankshaft in this position until the magneto
is installed.
NOTE
The advance timing mark is specified
on the engine nameplate.
Remove the inspection plug from the most convenient
side of magneto housing and plug from the rotor view-
ing location in the center of the housing. Rotate mag-
net drive shaft in normal direction of rotation until
the painted tooth on large distributor gear is centered
in the timing hole. The shaft on the impulse coupling
magneto
can be turned by depressing the pawl on the
coupling.
Observe that at this time the built in point-
er just ahead of the rotor viewing window aligns with
the "L" mark on the rotor. Be sure the magneto
gear does not move from this position and secure
magneto finger tight. The magneto is now ready for
final timing.
MODELS 112TC/TCA. FINAL TIMING. Attach red
lead from the timing light to left switch adapter lead,
green lead of timing light to right switch adapter
lead and the black lead of the timing light to the
magneto housing. Rotate the magneto in its mounting
flange
to a point where the red timing light comes on,
then slowly turn it in the opposite direction until the
red light goes out indicating the left main breaker
has opened. Then evenly tighten the magneto mount-
ing
clamps. Back the crankshaft up approximately
10 degrees, the timing light should come on. Bring
the crankshaft slowly back in direction of normal ro-
tation until the timing marks are in alignment, the
red light should go out indicating left main breaker
opening. The right main breaker, monitored by the
green light, must open within ~ 2 degrees of the num-
ber one firing position.' If the right breaker does not
open within the two
degrees tolerance, back the engine
up a few
degrees and again bring the crankshaft slowly
back
in direction of normal rotation toward number
one cylinder firing position while observing timing
lights. Adjust breakers to open (timing lights out)
when
the timing pointer is indicating within the width
of
the "L" mark. After adjusting breakers recheck
timing.
NO'l1
Some timing lights operate in the reverse
manner as described. Check your timing
light instructions.
IGNITION HARNESS
The ignition harness for each engine consists of eight
shielded high tension cable assemblies. Two of the
four cables from the left magneto are routed to the
upper spark plugs on the left bank of cylinders, while
the
other two cables from the left magneto are routed
to the lower spark plugs on the right bank of cylinders.
Two of the four cables from the right magneto are
routed to the upper spark plugs on the right bank of
cylinders, and the balance of the cables from the
right magneto are routed to the lower spark plugs on
the left bank of
cylinders (see Figure 4- 3).
CABLE
REMOVAL AND INSTALLATION. Ignition
cables may be removed individually or the ignition
harness may be replaced as a complete unit.
4-5
Copyright Commander Owners Group 2013 All Rights Reserved
**unofficial copy**