D330, D333, 3304, 3306 – Solid State Ignition

1. Transformer. 2. Wiring harness. 3. Spark plug cover. 4. Solid state magneto. 5. Timing bolt.

The solid state ignition system consists of five basic components: a solid state magneto, ignition transformers for each cylinder, wiring harness, spark plugs and engine instrument panel. The transformers, wiring harness and spark plugs are covered in basic engine information.

Instrument Panel
The instrument panel contains a magnetic switch, manual stop switch (1), oil pressure gauge (2), and a water temperature gauge (5) which are connected to the magneto.

In the event of normal stopping, high water temperature or low oil pressure, the magnetic switch is energized and interrupts the magneto output, this stopping the engine. On solid state systems a different magnetic switch is required to carry the higher output of the magneto.

1. Stop switch. 2. Oil pressure gauge. 3. Magnetic switch reset button. 4. Oil pressure gauge reset button. 5. Water temperature gauge.

Before cranking a cold engine, the magnetic switch and oil pressure gauge reset buttons (3) and (4) should be pushed in. This overrides grounding the magneto as is usual in the case of low oil pressure. Normal oil pressure releases the lock out and the gauge switch is ready to signal a shut down in case of low oil pressure.

When the water temperature gauge switch is operating properly, a hot engine cannot be started until the engine has cooled. Holding in the magnetic switch reset button will override the oil pressure and water temperature gauge switches.

The solid state magneto is a self-contained electric generating unit. Current is produced in the alternator section of the magneto (right hand side). Current is stored in the capacitor and released, then distributed through the circuit board in the pulser distributor section (left hand side). This system uses capacitive storage and low tension distribution.

Two moving parts, the magnet rotor and pulser rotor shaft both rotating on ball bearings will give long service life. Engine timing will remain as set, because no mechanical rubbing or wearing parts exist that cause gradual timing changes.


The solid state magneto utilizes non-wearing electronic switching to handle high surge currents and insures ignition at the highest of combustion chamber pressures. With solid state ignition, energy storage and voltage stepup are accomplished separately by the use of electronic switching. This system eliminates breaker points, contactors, and brushes. There is no arcing and only minimum wear. An electromagnetic spark advance is used. An ignition spark of high intensity is produced to fire the air-fuel charge under all operating conditions.

The alternator creates a voltage as the magnet rotor is driven by the engine through a drive coupling. The alternating current is rectified and stored in a capacitor (4). A zener diode, on the power board, regulates the capacitor voltage level for proper firing. As the pulser rotor (8) passes each pulser coil (trigger circuit) (7), a triggering voltage is produced and sent to the electronic switch (silicon-controlled rectifier) (9) for the firing cylinder. The switch is then ‘turned on’ and allows the capacitor (4) to discharge, through the distribution board (5), the low voltage high current impulse to the ignition transformer. In turn, the transformer produces a high voltage low current impulse which is sent across the spark plug electrodes. This same process recurs as the pulser rotor passes each pulser coil.

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