Toyota 3R-B 1969, Repair Manual

Page: 188 / 193

I G N I T I O N S Y S T E M - Ignition Coil, High Tension W ir es 10-13
T h e ignition coil is utilized to transform the battery voltage to the high voltage
sufficient to spark a c ro s s the spark plug gap.
It is composed of the prim ary and secondary windings, and the latter is wound
to thousands of windings of v e r y fine w i r e . By this windings, the voltage is in­
c r e a s e to about 20,000 volts which is sufficient to spark a c ro s s the spark p lu g
gap without any difficulty.
T h e voltage generated in the secondary winding is strongest when the prim ary
circuit is opened because of the difference of speed of movement of the magnetic
lines of f o r c e .
When the b r e a k e r points a re closed, the current flow s through the prim ary wind­
ings causing magnetic lines of fo r c e to move away from the soft iron c o r e .
B e ca u s e of their attraction to the c o r e , they move relatively slo w . When the
prim ary circuit is opened, the magnetic line of fo r c e snap back to the c o r e b e ­
cause of their attraction to it.
Specifications:
P r im a r y voltage
P r im a r y resistance
S e co n d a ry resistance
S eco n d ary voltage
Weight
12 volts
3.7 ohms
Approximately 9,000 ohms
Sparking distance from center to three
negative electrod es should be m ore than 8
mm ( 0 .3 1 5 " ) at distributor revolution of 75
rpm and at 12 volts.
Sparking distance from center to three
-negative electrodes should be m ore than
6 mm (0 .2 3 6 " ) at distributor revolution of
3,000 rpm and at 12 volts.
Approximately 0 .7 kg (1 .5 l b s ) .
Rem oval
1. Disconnect the w i r e s connecting
to the ignition c o i l .
2. R em ov e the ignition coil retaining
b olts, and then re m o v e the ignition
c o i l .
Inspection
B e fo r e testing the coil, alw ays heat
the coil to normal operating tem pera­
ture .
1 . Check the prim ary resistance with
a tester.
T h e reading should be within 3.3
to 4 .3 ohms.
2. Check the secondary resistance.
T h e resistance should be within
8,400 ~ 9,200 ohms.
If the reading is not within the
specified resistance, the coil is
opened o r shorted.
3. Check the insulation resistance
between the case and the terminal
with a 500 volts megoohm m eter.
T h e insulation resistance should
be m ore than 100 megohms.
4. Check the secondary voltage with
a coil tester following the instruc­
tion manual of the tester furnished
by the manufacture.
T h e sparking distance from the
center to the three negative e le c ­
trodes should be m ore than 8 mm
( 0 . 3 1 5 " ) at distributor revolution
of 75 rpm and at 12 volts.
A l s o the sparking
than 6 mm (0.236*0 at distributor
revolution of 3,000 rpm and at
12 volts.