Cummins/Onan Onan P4500i Inverter / P4500 — Spark Plug Maintenance
Maintenance
For the Cummins/Onan Onan P4500i Inverter / P4500, from the Cummins/Onan operator's manual.
Applies to: Cummins/Onan P4500
Before you start
- NEVER apply any side load or move the spark plug laterally when removing it.
- Always use the Cummins OEM or compatible resistor-type spark plug.
Parts for this job
Part numbers from the service-parts list for Cummins/Onan P4500. Verify against your serial number before ordering; some links are affiliate links.
Procedure
- Place the generator on a level surface and allow the engine to cool.
- Remove the engine service cover.
- Remove the spark plug boot by pulling it directly away from the engine.
- Clean the area around the spark plug.
- Remove the spark plug with the included spark plug socket wrench.
- Inspect the spark plug; replace if electrodes are pitted, burned, or insulator is cracked.
- Measure the electrode gap with a wire-type feeler gauge; correct by bending the side electrode if needed.
- Install the spark plug finger tight, then tighten an additional 3/8 to 1/2 turn with the spark plug wrench.
- Install the spark plug boot and engine service cover.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Spark plug gap: 0.024 - 0.032 in. (0.60 - 0.80 mm)
- Inspect/clean every 100 hours or six months; replace after 300 hours or every year
Full service-parts list: Cummins/Onan P4500 →
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.