Ignition System Diagnostics

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Ignition System Diagnostics

• Reading A Scope Pattern

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The Scope
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FIRING ORDER
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FIRING ORDER

• Some older scopes read 1 cylinder to the far
  right

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Secondary Patterns

• 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

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Secondary Pattern
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NORMAL PATTERNS
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NORMAL PATTERNS

• 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

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Review
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A
B
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(No Transcript)
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(No Transcript)
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Spark Plug Under Load Test
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Abnormal Increase
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ABNORMAL PATTERNS
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Can Be Caused By

• Spark Plugs
• Coil
• Cap/Rotor
• Fuel Air Mixture
• Timing
• Compression

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Causes of Abnormal Patterns
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Low Cylinder Pressure
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Open Secondary Circuit
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Distributor Rotor Problems
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Low Secondary Resistance
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Raster Pattern
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Problems ?
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Cylinders 2 3
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Review
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(No Transcript)
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(No Transcript)
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Low Compression
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Low Compression
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Low Secondary Resistance
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Low Secondary Resistance
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Defective Coil
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Incorrect Air Fuel Mixture