Onan MJA Series Service Manual page 44

42
IGNITION SYS TEM
3.3.3 MJB IGNITION SYSTEM
This ignition system uses a single 4 volt coil, battery ignition to fire
both spark plugs simultaneously; this means one spark plug fires on the'
exhaust stroke while the other is firing at the end of the compression
stroke. A spark advance on the breaker point mechanism advances the
spark from 50 ATC (after top center) when cranked to 25 0 BTC (before>
top center) when running at rated speed and using
gasoline~
SPARK
SPARK
PLUG
PLUG
TOCONTROL
BOX TERM.
BLOCK
HIGHTEMP.
CUT OFF
SWITCH
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L_..., __ J
II
- - IGNITION
II
-=-
BREAKER
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II
POINTS-l
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- - 1 -
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FIG 3.3. B - MJB IGNITION SYSTEM
3.3. 3.1 Maintenance . - Operating with a weak spark is detrimental to
the generating plant, so periodic service is extremely important. Per­
iodic maintenance should include ­
-- checking the ignition breaker point gap.
i'
-- checking and cleaning .spark plugs.
~t,.
-- ins,pecting both the low and hi tension wiring.
-- checking the ignition timing.
To adjust the breaker gap, rotate the crankshaft clockwise until the
55
0
ATC mark on the flywheel matches the timing pointer (Fig 3.3. C).
This is the point of maximum breaker opening.
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