My Craftsman Mower Has a Weak Yellow Spark
- 1). Gap the spark plug. Locate the .030 gap paddle on the gapping tool and gap the spark plug to this specification. Test the plug for spark. If the plug still shows a weak yellow spark, go to the next step.
- 2). Replace the plug with a brand new one that's specifically made for your mower. They are available at virtually every hardware store. Gap the plug to .030 and test the plug. If there is still a weak yellow spark, proceed to the next step.
- 3). Check the spark plug wire for breaks or cracks. A broken or cracked spark plug wire will short circuit against the metal engine housing, metal frame or any other metal piece it runs next to. Replace the wire if any cracking or breaking is noticed. Once replaced, test the spark plug. If there is still a weak spark, go to the next step.
- 4). Replace the coil/ignition module. On older lawn mowers, there will be an actual engine coil that sends electricity to the plug through the wire. On newer engines, the coil has been replaced by an ignition module. They both do virtually the same thing. Pull the spark plug wire off of the coil/ignition module, remove the wires from the battery and unbolt the unit from the lawn mower frame. The coil/ignition module unit can be found at hardware stores or small engine repair places. Always take the old one in to match it up precisely with a new one. Attach the new one to the mower in the same way that it came off and check the plug.
Source...