Onan MJA Series Service Manual page 48

46
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4. Install tbe breaker plate.
Install tbe ignition plung­
er and diaphragm and
diaphragm cup, Fig 3.3.
G.
5. Install the start-discon­
nect (when used) dia ­
pnragm and plunger,
and install the start ­
disconnect breaker pOints.
6. Adjust the start-discon­
nect breaker point gap
(if
used) to. 020 in.
7. Install the ignition break ­
er pOints and adjust the gap, Sect 3. 3. 3. 1.
8. Time the ignition, Sect 3.3.3.2.
3.3.3.4 Condenser. - The .3 mfd condenser mounted on the breaker
plate aids primary field breakdown when the points open and prolongs
the life of the breaker points by reducing the arc across them. A de ­
fective condenser causes a weak spark and rapid breaker point wear.
Use a standard cOmmercial condem;er checker to test the condenser
for leakage, openings or grounding. If nO tester is available, check for
shorts or defective leads and replace the condenser if you suspect it has
defects.
3.3.3.5 CoiL -
If
spark is weak or there is no !Spark, and the breaker
pOints are clean and properly adjusted, test the coil for possible defects.
As a general test of the coil, disconnect the spark plug lead(s), ground
one
(if
2 leads), and hold the lead (second lead
if
dual terminal coil)
1/4 inch from the engine. Then crank the engine. A good spark indi­
cates the coil is operating.
Further tests of the coil are as follows:
1. With an ohmmeter check the resistance of the coil windings. Nor ­
-l
mal resistance readings range from. 5 - 2 ohms for the primary
Winding and from 4000 - 10000 ohms for the secondary winding.
E.~'tremely
low resistance usually indicates a shorted winding and
extremely high resistance usually indicates an open in the winding.
WARNlNG: The 4 volt coils (MJB, MJC) can be tested on a 6 volt
tester. However, a 12 volt tester will destroy the coil
in a few seconds.
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FIG 3.3.G - lNS TALLlNG
IGNITION PLUNGER