Ignition System - Stihl 029, 039 Service Manual

STIHL 029, 039
2.3

Ignition System

Warning: Exercise extreme caution while carrying out maintenance and repair work on the ignition system.
The high voltages which occur can cause serious or fatal accidents!
Remove spark plug.
Is it in good condition?
Clean spark plug and reset electrode gap.
Does spark test produce powerful spark?
Is air gap correct?
Adjust air gap (0.15 - 0.3 mm).
Is spark test positive?
Use ohmmeter to check ignition lead
for break. If break is detected, replace
ignition lead. Does spark test now
produce sparkover?
Replace ignition module. Does engine
now run after positive spark test?
Spark plug terminal firmly seated on spark plug?
yes
yes
no
no
Replace faulty ignition lead of short circuit wire.
Repair contact spring or switch shaft.
Insert screwdriver in place of spark plug in spark plug
terminal and hold about 4 mm (1/8") away from
ground. Sparkover?
no
yes
no
no
no
no
no
no
Press terminal firmly onto spark
plug and fit spring if necessary.
Faulty insulation on ignition
lead or short circuit wire?
Is connector sleeve touching short circuit
contact?
yes
yes
Fit new spark plug.
Does flywheel appear to be
in good condition?
yes
Fit new flywheel.
Is spark test positive?
Ignition system in order.
Look for fault in fuel system and
carburetor.
9
no
no