Cummins/Onan B43 / B48 — Ignition Coil Test
Testing & diagnosis · ignition system
For the Cummins/Onan B43 / B48, from the Cummins/Onan service manual.
Applies to: Cummins/Onan B48
Procedure
- Make sure ignition power is off and coil is at room temperature of 70 deg F (21 deg C).
- Use a Simpson 260 VOM or equivalent.
- Place black lead on negative (-) terminal of coil and red lead to positive (+) coil terminal; primary resistance should read between 3.87-4.73 ohms.
- Change resistance setting on ohmmeter; place ohmmeter leads inside of spark plug cable holes; secondary resistance should read 12,600-15,400 ohms.
- If any of the above conditions are not met, replace coil.
Tools required
- Simpson 260 VOM or equivalent Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Primary resistance 3.87-4.73 ohms
- Secondary resistance 12,600-15,400 ohms
Full service-parts list: Cummins/Onan B48 →
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.