Outdoor Power Equipment, Small Engine, Lawn Mower Repairs, Troubleshooting and Safety

The ignition system on this engine is extremely simple. It starts with an ignition coil (also called ignition armature, lamination, module, solid-state) set at a gap of 0.006-0.010 in. (other models typically from 0.006 to 0.014 in. - see Briggs & Stratton Ignition Armature Air Gaps) from the flywheel magnet.

#1 shows the gap being set with a shim of appropriate thickness while the magnet is aligned with both legs of the coil.

A kill wire is attached to the underside of the coil as shown in #2. When the other end of this wire is grounded, no spark will be sent to the spark plug.

The other end of the kill wire is attached to clip on the underside of the control bracket (#3).

#4 shows that the kill switch itself is nothing more than a contact blade that is grounded when contacted by the control lever.

If the flywheel key is sheared, the spark will occur at the wrong time but it will still be present. Refer to the article on #5.

Check that the flywheel magnet is secure. Check its magnetism by suspending a screwdriver an inch away from the magnet (#6). If the magnet draws the screwdriver to itself, the magnet is good.

To check for spark, remove the spark plug from the head, and connect the spark plug wire to it. Being sure that there is no gas spilled in the area. Hold the plug to a clean ground on the block and pull the starter rope. A bright blue-white spark should jump the plug electrodes (#7). As a further test you can hold the plug about 3/16 in. from the block (#8). A good strong coil will supply a spark that jumps this distance.

If you have no spark, and the spark plug is good, and the flywheel magnet is good, and the gap between the coil and magnet is correct, and the kill wire is disconnected from the coil, and the coil is securely mounted to the block, then the coil is bad.