Cummins/Onan B43 / B48 — Timing Test (Continuity)
Testing & diagnosis · Ignition timing
For the Cummins/Onan B43 / B48, from the Cummins/Onan operator's manual.
Applies to: Cummins/Onan B48
Procedure
- Adjust breaker points.
- Remove blower housing to expose timing marks on top of gearcase cover and flywheel.
- Rotate flywheel clockwise until timing mark aligns with the mark corresponding to 16° BTC on top of gearcase cover.
- Connect an ohmmeter or continuity test lamp across the ignition breaker points; touch one prod to the coil lead terminal.
- Touch the other test prod to a good ground on the engine.
- Turn crankshaft counterclockwise until points close, then slowly turn clockwise.
- Lamp should go out (continuity lost) just as points break. If timing early the gap is too large; if late too small. Adjust accordingly.
Tools required
- Ohmmeter or continuity test lamp Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 16° BTC timing mark
Full service-parts list: Cummins/Onan B48 →
Source: Cummins/Onan operator's 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.