Stihl MS 440 - Ignition System Troubleshooting

51MS 440, MS 440 C
7.6 Ignition System Troubleshooting
Engine does not run
Master Control lever
or separate stop switch
in position “#“?
Check the spark plug:
– Smeared with oil, black?
– Sooted?
– Electrode gap correct?
– Contacts shorted?
Clean the plug, reset
or replace
Check spark plug boot:
– Firmly seated on plug (leg spring)?
– Leg spring hook in center of ignition lead?
– Boot damaged?
If necessary, install new spark plug boot
and/or leg spring
Test ignition system with
ZAT3 or ZAT4
(use ZAT 3 as main spark gap
– see TI 32.94)
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