Briggs & Stratton Ignition Troubleshooting

Updated February 21, 2017

Briggs & Stratton is a company that has built a solid reputation as a manufacturer of quality small gasoline engines. Briggs & Stratton engines are used by other manufacturers to power diverse equipment such as lawnmowers, snowblowers, line trimmers, chain saws, portable generators and a host of small recreational vehicles. Briggs & Stratton engines manufactured since 1982 have incorporated the proprietary Magnetron ignition armature, an upgrade from a points-and-breaker system and greatly simplifies ignition troubleshooting.

Check that the spark plug leads connect solidly to the spark plugs. Push firmly on the rubber boot of each spark plug lead to be sure the contactor clip is making firm contact with the spark plug. If the connection seems loose, pull the lead from the spark plug and squeeze the contactor clip with pliers to tighten it. Reattach the lead to the spark plug and confirm that the connection is now sound. Repeat this process for each spark plug.

Remove the spark plugs from the engine. Verify that the plugs are clean and the gap is set according to the manufacturer's specification. Regap or replace spark plugs as necessary.

Check the engine cut-off switch to be sure it is in good condition and functions properly. Be sure all wires are in good condition and all contacts are sound. Be sure the switch is not dirty or corroded. Replace the switch if it is defective.

Remove each spark plug from the engine, one at a time, and then reattach the lead to the removed plug. Touch the spark plug side electrode firmly to a metal engine part and crank the engine. As the engine rotates, a strong blue spark should be visible flashing in the spark plug gap.

Check the condition of the flywheel magnet and the magneto coil. Be sure that all wires are in good condition and properly attached. Closely check the magneto windings to be sure they are in good condition. If the windings are damaged, then replace the magneto. Remove any dirt or deposits on the magnet or magneto by rubbing lightly with fine emery paper. Check the air gap between the magnet and magneto. If the gap is incorrect then loosen the retaining screws on the magneto and adjust it inward or outward as appropriate to correct the gap.

Check the flywheel key to be sure it is not bent or damaged. Misalignment between the flywheel and the crankshaft will cause a timing error in the ignition spark. If the key is damaged in any way, it should be replaced.

Things You'll Need

  • Spark plug socket
  • Feeler gauges
  • Pliers
  • Screw drivers
  • Fine emery cloth or emery paper
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