Stihl MS 171 Manual page 14

Condition
No spark
MS 171, MS 181, MS 211
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Cause
Spark plug faulty
Faulty insulation or short in short
circuit wire
Break in ignition lead or insulation
damaged
Ignition module faulty
Remedy
Install new spark plug
Check short circuit wire for short
circuit to ground
Check ignition lead, replace ignition
module if necessary
Install new ignition module
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