How to Replace Coils in a Craftsman Lawnmower

The coil on your Craftsman lawnmower sends an electrical signal from the ignition to the spark plug. The ignition times the spark from the coil to coincide with the piston's movement to TDC-top dead center. The spark ignites the fuel and air inside the combustion chamber and forces the piston back down to BDC-bottom dead center. When the coil wears out, the electrical spark weakens. Eventually the spark is too weak to ignite the fuel and air inside the combustion chamber and the engine fails to start. You do not have to be a small engine mechanic to replace a coil.

Wrench
Screwdriver

Instructions

- 1
  Disconnect the negative battery cable form the battery terminal with a wrench. Disconnect the positive battery cable. Position both cables so they cannot touch the terminals on the battery.
- 2
  Locate the spark plug wire under the engine hood. The spark plug wire connects to the spark plug, which secures to the side of the engine's cylinder. The wire is black and approximately ¼ inch in diameter.
- 3
  Trace the spark plug wire away from the cylinder to the coil. The wire plugs into the coil. Pull the spark plug wire's boot off the coil with your fingers, then unplug the wiring harness that connects to the coil.
- 4
  Remove the screws that secure the coil to the engine and discard the old coil.
- 5
  Place the new coil onto the engine and secure it with the original screws.
- 6
  Plug the wiring harness into the coil and then press the spark plug wire's boot onto the coil.
- 7
  Reconnect the battery cables to the battery. Connect the positive cable and then the negative battery cable.

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