1. Ignition Systems
Chapter 9: Part 2

2. Ignition Coil: Composition

3. Ignition Coil: Composition

5. Spark Plugs Come in a variety of configurations
Each type is manufactured for a desired outcome
Very specific tolerances
Contain many of the same parts across plug types

6. Spark Plugs: Parts

7. Plug Leads Exposed Clip Connector Advantages
Less expensive to manufacture
Easy to add a “Kill Switch”
Disadvantages
Exposed to dirt, oil, moisture, animals
Easy to ground accidently
Can lead to arching or flashover

8. Plug Leads Advantages Boot Type Connector Virtually eliminates arching
Reduces flashover
Protects terminal nut from debris
Disadvantages
Higher manufacturing cost
Requires another type of “Kill Switch”
Not as easy to remove

9. Spark Plug Reach Correct length must be selected
To long = piston damage
To short = poor combustion

10. Spark Plugs: Parts

12. Spark Plug Reach Long Reach Cylinder Short Reach Cylinder

13. Find your Kohler spark plug. Find your paper in file cabinet
Find your Kohler spark plug. Find your paper in file cabinet. Grab a Champion Spark Plug Chart. (On the podium) Use chart to “decode” your plug.

14. Reading Plugs

15. Reading Plugs: Champion

16. Plugs and Manufacturers
wapedia.mobi

17. Plug Heat Transfer Plugs must deal with heat
All plugs have a heat range: from HOT to COLD
Insulator nose size helps regulate plug temp
Plug needs to match specific engine

18. Spark Plug Heat Transfer
HOT
COLD
Insulator nose is longer
Less likely to ‘foul’ from carbon deposits
Using a plug that is to hot can result in engine failure
Shorter insulator nose
Transfer heat quickly
Used in engines with HIGH COMBUSTION temps
Note: the hottest part of the plug is the tip of the insulator!

19. Spark Plug Heat Transfer
HOT
COLD

20. How do they measure plug temps?
Thermocouple Plug

21. Gapping Plugs Gap refers to space between electrode tip
Specific to engine type in conjunction with correct plug selection
Must be installed to manufacturers specifications

22. Gapping Plugs: measure then bend
1. Verify dimension with specs 2. Check gap 3. Use notched end to bend to desired clearance

23. Most common gap
.030”

24. Electrode Designs
Most common

25. Electrode Designs

26. Electrode Designs

27. Problems with Spark Plugs
Flashover
Bridging
Fouling
Detonation
Worn electrode
Melted

28. Flashover

29. Bridging Accumulation of deposits on the electrode Can be caused by:
Oil inside the combustion chamber
Plug is the wrong temp range
Can also be caused by fuel additives

30. Carbon Fouling Carbon deposits can build up on the electrode
This eventually causes a conductive path from electrode to the ‘reach’ (threading)
Plug continues to ‘fire’ but spark does not occur
Causes: rich fuel mixture and or cold plug

31. Detonation VERY BAD!! Can cause severe engine damage!
Looks like bits of pepper on the electrode
Fuel is not completely detonating
Causes:
Improper octane fuel
Incorrect timing
Wrong plug temp

32. Worn Electrode Note the rounded electrode Plug needs to be replaced
Simply worn out
Replace with correct plug to manufacture specifications

33. Melted Electrode Oops Potential causes: Wrong Plug
Timing to early
Faulty distributor
Wrong Plug
Not commonly found on single cylinder engines
Check engine manufacture specifications and replace immediately

34. Review: Parts