IGNITION SYSTEM
49
Troubleshooting the ignition system
The purpose of the ignition system is to provide a
spark in the combustion chamber at the proper time to
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 chap
-
ter.
NOTE: It is convenient to check the compres-
sion when the spark plug is removed for exami-
nation.
2. Connect a spark tester between the spark plug
wire and a good ground point on the engine.
See Figure 7.1.
Figure 7.1
Spark tester
NOTE: It only takes 1,000 volts to jump a .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. Insert key and move throttle to the full throttle
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 sys
-
tem. 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 testing is required.
6. Test the stop switch by following the steps
described in the stop switch section of this chap
-
ter.
7. If the stop switch is working properly, inspect the
flywheel and flywheel key. If the flywheel and
key are OK, replace the module.
! CAUTION! CAUTION
Never remove the spark plug and
hold it against the cylinder head to
test for spark. The fuel/air mix
coming out of the spark plug hole
will catch on fire.
CHAPTER 7: IGNITION SYSTEM
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