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Ignition System
81
Troubleshooting the ignition system
The purpose of the ignition system is to provide a spark
in the combustion chamber at the proper time to efficiently
ignite the fuel/air mixture. The steps in troubleshooting the
ignition system are:
1. Examine the spark plug(s) by following the steps
described in the spark plug section of this chapter.
NOTE: It is convenient to check the compression when the
spark plug is removed for examination.
2. Connect a spark tester between the spark plug wire
and a good ground point on the engine.
See Figure 7.1.
NOTE: It only takes 1,000 volts to jump a 0.025” air gap in open atmosphere, it takes 10,000 volts to jump the
same gap at 120 psi; therefore, an open air spark test in not valid.
NOTE: The spark should be a minimum of 10 Kv (10,000 volts) at pull over speed.
3. Make sure any remote stop switch is turned to the “run” position.
4. Pull the starter rope. If sparks can be seen in the spark tester, the ignition system is working.
NOTE: If there are sparks present in the spark tester, install a known-good spark plug and prime test the
engine. If the engine does not start, check the fly wheel key. If the fly wheel key is intact, the problem is
not in the ignition system. Check the engine’s compression.
5. If no sparks or weak sparks are seen in the spark tester, use the electric starter to spin the engine.
NOTE: If sparks are now seen in the spark tester, check the module air gap. If no sparks are seen, further test-
ing is required.
6. Test the stop switch by following the steps described in the stop switch section of this chapter.
7. If the stop switch is working properly, inspect the flywheel and flywheel key. If the flywheel and key are OK,
replace the module.
Figure 7.1
Spark tester
! CAUTION! CAUTION
Never remove the spark plug and
hold it against the cylinder head to
test for spark. The fuel/air mix com-
ing out of the spark plug hole will catch on fire.
CHAPTER 7: IGNITION SYSTEM
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