Cummins/Onan — Ignition System Testing
Testing & diagnosis · Electronic battery ignition system
From a Cummins/Onan service manual covering: P216, P218, P220, P248. Check it applies to your exact model before use.
Applies to: Cummins/Onan P216, Cummins/Onan P218, Cummins/Onan P220, Cummins/Onan P248
Before you start
- The electronic ignition produces voltage which can cause electrical shock. Do not touch electrical components or wires while ignition is on.
- Accidental starting of the engine can result in severe personal injury or death. Remove spark plugs before proceeding.
- Ignition of cylinder gases can cause severe personal injury. Ground spark tester away from spark plug holes.
- Do not attach any lead or jumper with power (such as B+) to coil negative terminal.
Procedure
- Check all electrical connections to be sure they are clean and tight; if good, go to Step 2.
- Test the ignition coil for proper resistance; if good, go to Step 3.
- Pull the spark plug wires off the spark plugs and remove the spark plugs.
- Connect an approved spark tester to each spark plug wire and ground them away from the spark plug holes.
- Turn the key on and crank the engine for 5 seconds while watching for spark; regular spark means the problem is not in the ignition system.
- Connect a jumper lead from the positive battery terminal to the positive (+) coil terminal (smaller diameter post) and crank while watching for spark.
- If no spark, connect the positive probe of a 12-volt test light to the negative (-) coil terminal (larger post) and the negative probe to a good engine ground.
- Turn the key to START; the test light should flash on and off; if it stays on or does not light, replace the ignition module.
- If the trigger ring was removed, reinstall it with the part number side readable (facing the flywheel); do not push the ring up against the seal.
- Install the spark plugs and wires; connect the red lead from a new module to the positive (+) coil terminal and the black lead to the negative (-) terminal.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Crank engine over for 5 seconds while watching for a spark
Full service-parts list: Cummins/Onan P216 →, Cummins/Onan P218 →, Cummins/Onan P220 →, Cummins/Onan P248 →
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.