Cummins/Onan — Ignition Coil Test
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Procedure
- Remove all wires attached to the ignition coil.
- Remove the coil from the engine.
- Inspect the terminals for corrosion, looseness, cracks or other damage.
- Clean the outside of the coil with a cloth dampened in parts cleaning solvent.
- Measure primary coil resistance across the positive and negative terminals.
- Measure secondary coil resistance across the spark plug cable terminals.
Tools required
- Ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Primary resistance 3-5 ohms
- Secondary resistance 14,000-30,000 ohms
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.