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Some pictures and slides courtesy of Jerry Delena MCVTHS Thanks Jerry

Some pictures and slides courtesy of Jerry Delena MCVTHS Thanks Jerry. Will need Pinto and scope. Chrome. Scope connection. Red (trigger). #1 spark plug. Blue. Black to common. Not an acceptable use of a scope . Scope Screen. V O L T A G E. T I M E. Scope Screen. Voltage is

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Some pictures and slides courtesy of Jerry Delena MCVTHS Thanks Jerry

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  1. Some pictures and slides courtesy of Jerry Delena MCVTHS Thanks Jerry Will need Pinto and scope

  2. Chrome Scope connection Red (trigger) #1 spark plug Blue Black to common

  3. Not an acceptable use of a scope

  4. Scope Screen

  5. V O L T A G E T I M E Scope Screen Voltage is usually in thousands of volts (KV) Time can be in degrees of rotation or in milliseconds (mS) All vertical lines represent a change in voltage All horizontal Lines represent a change in time

  6. Scope Screen 0 to 5000 volts over no time

  7. Scope Screen 0 to 5000 volts over little time

  8. Scope Screen 0 to 5000 volts over more time

  9. Scope Screen 5000 to 6000 volts over long time

  10. Scope Screen 6000 volts steady over length of time screen is set for

  11. Scope Screen Steady 6000 to 0 volts over no time

  12. Secondary Patterns • Display actual voltage needed to fire each spark plug (firing voltage) • Duration of each spark (spark line) • Coil condition (oscillations) • Displayed two different ways • Display or Parade • Raster

  13. Parade or Display Parade pattern Time on screen represents Two revolutions of Crankshaft or (7200)

  14. Raster Raster pattern Time on screen represents maximum Dwell time 8 cyl = 450 6 cyl = 600 4 cyl = 900

  15. Points open Here or Transistor Turns off Secondary pattern Firing voltage 5-14KV Maximum of 3 KV difference between cylinders 0 volts Firing Section Dwell Section Intermediate Section

  16. Spark starts here Spark stops here Secondary pattern Firing voltage 5-14KV 0 volts Firing Section Dwell Section Intermediate Section

  17. Coil saturation Magnetic field starts building in coil primary Secondary pattern Firing voltage Spark line Coil oscillations (coil condenser with points) Points close or transistor turns on here 5-14KV .5-2.5KV 0 volts Firing Section Dwell Section Intermediate Section

  18. Points open or transistor turns off here starting the process over for the next cyl. Secondary pattern Firing voltage Spark line Coil oscillations (coil condenser with points) Points close or transistor turns on here 5-14KV .5-2.5KV 0 volts Firing Section Dwell Section Intermediate Section

  19. Firing Order 1-8-4-3-6-5-7-2 Starts from where you hook up the red trigger pick-up M U S T K N O W Raster Parade Same pattern displayed differently

  20. FIRING ORDER • Most older scopes shift # 1 cylinder to the far right • Some scopes you can shift it back

  21. Let’s go demo what we have learned so far

  22. Which is numbered correctly for a firing order of 1-3-4-2 ? A B

  23. Look for firing voltage to be within 3 KV of each other Look for spark lines to be a reasonable amount (500 – 2500 V) Firing section (parade) Look for firing voltage to be a reasonable amount (5 – 14 KV) Look for straight up firing voltage lines

  24. Factors that affect firing voltage The voltage induced into secondary winding only rises enough to push current across the air gaps Rotor air Gap .060 - .100” Spark Plug Gap .030 - .080”

  25. Factors that affect firing voltage Once the gaps are ionized, (current flowing) it only takes a couple KV to keep current flowing

  26. Factors that affect firing voltage X X I was taught that this was a series circuit and all the resistance added up to determine the firing voltage X X X X X X X X

  27. Factors that affect firing voltage New theory is called “The Dominating Gap Theory” Remember spark plug is under compression when it fires Rotor air Gap .060 - .100” Spark Plug Gap .030 - .080”

  28. Factors that affect firing voltage Cylinder pressure A/F mixture Turbulence Any gap or break in circuit that acts greater than plug Dominating gap theory “Greatest gap theory”

  29. Can’t see firing voltage very well displayed this way! Firing section (raster) Look for length and angle of spark lines Length should be between .8 – 2.2 mS

  30. Secondary patternFiring section

  31. Secondary patternFiring section What it shows wrong with ignition system? Normal Grounded plug wire Narrow plug gap 10 KV 3 KV Compare 1.5 mS 2 KV 2.5 mS .5 KV What is wrong about the pattern? Too low firing voltage Too long spark line

  32. Spark Plug Under Load Test Snap throttle Cylinder pressure goes up Mixture goes lean KV should all go up about the same On deceleration Cylinder pressure goes down Mixture goes rich KV should all go down about the same

  33. Secondary patternFiring section What it shows wrong with ignition system? Normal Wide gap (plug, plug wire coil wire/rotor if on all cylinders) 10 KV Compare 1.5 mS 2 KV 18 KV What is wrong about the pattern? Too high firing voltage Too high spark line voltage Too short spark line .7 mS 5 KV

  34. Snap throttle test Has to be inside cylinder If it does this on acceleration

  35. Think of the firing voltage line and spark line as a string • It you use more of it on the firing voltage line you will have less for the spark line

  36. Secondary patternFiring section What it shows wrong with ignition system? Turbulence (burnt valve, wild cam) Next one down 12 KV 1.5 mS What is wrong about the pattern? 2 KV Spark line is too rough

  37. Downward spike should be about ½ of firing KV showing good coil insulation Secondary patternFiring section What it shows wrong with ignition system? 22 KV Plug wire off (no spark) Next one down This is how we check for Maximum coil output What is wrong about the pattern? Firing KV too high No Spark line -11 KV

  38. Secondary patternFiring section What it shows wrong with ignition system? Very wide plug gap Wire part way off or broken Next one down 20 KV .3 mS 15 KV What is wrong about the pattern? Firing KV too high Spark line is too high Spark line too short

  39. Secondary patternFiring section What it shows wrong with ignition system? Points arcing when opening Second one down On the right What is wrong about the pattern? Firing line not straight up

  40. Secondary patternFiring section What it shows wrong with ignition system? Very narrow plug gap (fouled plug) Wire jumping to common (snap test) Next one down 3 KV 3.5 mS .5 KV What is wrong about the pattern? Firing KV too low Spark line too long

  41. Secondary patternFiring section What it shows wrong with ignition system? Lean mixture Next one down 14 KV .8 mS 2 KV What is wrong about the pattern? Spark line tapers up on end

  42. Secondary patternFiring section What it shows wrong with ignition system? Intermittent miss (plug or Wire jumping to ground) Last one 12 KV .8 mS 2 KV .5 KV What is wrong about the pattern? Spark line keeps changing length And height

  43. Comparing display and raster

  44. Secondary patternRaster (intermediateand dwell section)

  45. Secondary patternRaster (intermediate and dwell section) Normal raster patern 1.5 mS

  46. Secondary patternRaster (intermediate and dwell section) Normal raster pattern 1.5 mS What is wrong about the pattern? Point close line not straight down Point opening line not straight up What about the ignition system that would cause this kind of problem Points arcing when closing and opening

  47. Secondary patternRaster (intermediate and dwell section) Next one down What is wrong about the pattern? Not enough coil oscillations No oscillations when field saturates What about the ignition system that would cause this kind of problem Bad coil

  48. Secondary patternRaster (intermediate and dwell section) Next one down Same as above only worse

  49. Secondary patternRaster (intermediate and dwell section) Next one down What is wrong about the pattern? Dwell section is not flat after saturation What about the ignition system that would cause this kind of problem Loose primary connection

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