Cummins/Onan P2400 / P3500 — Spark Plug Service
Maintenance · Ignition system
For the Cummins/Onan P2400 / P3500, from the Cummins/Onan service manual.
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Before you start
- The spark plug and engine will be very hot if the engine has been running.
Procedure
- Turn off the generator set and allow it to cool off.
- Remove the spark plug cap and clean any dirt from around the spark plug base.
- Use the wrench supplied in the tool kit to remove the spark plug.
- Visually inspect the spark plug; discard if the insulator is cracked or chipped; clean with a wire brush if reused.
- Measure the plug gap with a feeler gauge and correct by carefully bending the side electrode.
- Verify the spark plug washer is in good condition and thread the spark plug in by hand.
- After the spark plug is seated, tighten with a spark plug wrench to compress the washer.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Tighten a new spark plug 1/2 turn after seating.
- Tighten a reinstalled used spark plug 1/8-1/4 turn after seating.
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.