Ignition System Diagnostics
Reading A Scope Pattern
FIRING ORDER
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Some older scopes
read # 1 cylinder to
the far right
Secondary Patterns
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Most often used
Are read in Parade or Raster
Display actual voltage needed to fire
each spark plug
Duration of each spark
Coil condition
Secondary circuit resistance
NORMAL PATTERNS
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FIRING LINES HAVE 7 THOUSAND TO
10 THOUSAND VOLT RANGE
NO MORE THAN 3,000 VOLT
DIFFERENCE BETWEEN CYLINDERS
KV IS AN ABBREVIATION FOR
THOUSAND VOLTS
Review
Spark Plug Under Load Test
Can Be Caused By
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Spark Plugs
Coil
Cap/Rotor
Fuel Air Mixture
Timing
Compression
Distributor & Rotor Problems
Cylinders # 2 & # 3
Review
Low Compression
Low Compression
Low Secondary Resistance
Low Secondary Resistance