Cub Cadet MTD 70 Series - Manual (Page 87)

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
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 exam-
ination.
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 .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. Place the stop switch in the run position (Insert key for snow engines and move throttle to the full throttle posi-
tion).
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, the problem is not in the ignition system. Check the engine’s com-
pression.
5. If no sparks are seen in the spark tester further testing 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, replace the module.
8. Inspect the flywheel.
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