Cummins/Onan — Testing Ignition Coil
Testing & diagnosis
From a Cummins/Onan service manual covering: 4CCK, 5CCK, 5CCK-150R, 5CCK-3CR. Check it applies to your exact model before use.
Applies to: Cummins/Onan 4CCK, Cummins/Onan 5CCK, Cummins/Onan CCK engine
Before you start
- A 12-volt tester will destroy a 6-volt coil in a few seconds; do not leave coil on tester over 15 or 20 minutes
Procedure
- Disconnect the spark plug leads and ground one.
- Hold the second lead 1/4 in. from the engine.
- Crank the engine; a good spark indicates the coil is operating.
- Check primary winding resistance with an ohmmeter (0.5 to 2 ohms).
- Check secondary winding resistance (4,000 to 10,000 ohms).
- Replace coil if extremely low (short) or extremely high (open) resistance.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Primary 0.5-2 ohms; secondary 4,000-10 Amazon eBay FridayParts $37.99,000 ohms
Full service-parts list: Cummins/Onan 4CCK →, Cummins/Onan 5CCK →
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.