Chapter 7 Ignition; Solid State Ignition; Solid State Ignition Operation; Spark Plug Service - Tecumseh VLV Technician's Handbook

Solid State Ignition

Tecumseh's solid state capacitor discharge ignition
(CDI) is an all electronic ignition system and is encap-
sulated in epoxy for protection against dirt and mois-
ture.

Solid State Ignition Operation

As the magnets in the flywheel rotate past the charge
coil, electrical energy is produced in the module. This
energy is transferred to a capacitor where it is stored
until it is needed to fire the spark plug.
The magnet continues rotating past a trigger coil where
a low voltage signal is produced and closes an elec-
tronic switch (SCR).
The energy which was stored in the capacitor is now
transferred through the switch (SCR) to a transformer
where the voltage is increased from 200 volts to 25,000
volts. This voltage is transferred by means of the high
tension lead to the spark plug, where it arcs across the
electrode of the spark plug and ignites the fuel-air
mixture.

Spark Plug Service

Spark plugs should be replaced periodically. Check
electrode gap with wire feeler gauge and adjust gap to
.030" (.762 mm). Replace if electrode is pitted, burned
or the porcelain is cracked. Refer to Master Parts
Manual for correct replacement number. Use a spark
plug tester to check for spark.
If spark plug fouls frequently, check for the following
conditions:
1. Incorrect spark plug
2. Poor grade gasoline
3. Breather plugged
4. Oil level too high
5. Engine using excessive oil
6. Clogged air cleaner
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Chapter 7
Ignition
7-1