Cummins/Onan — Spark Plug Removal
Repair & overhaul · Ignition system
From a Cummins/Onan owner's manual covering: GTA8.3, GTA8.3 CD1, GTAR 3. Check it applies to your exact model before use.
Applies to: Cummins/Onan GTA8.3 engine
Before you start
- Do not touch the porcelain area on the spark plug.
Procedure
- Disconnect the wires from the ignition coil end first and then from the spark plug end.
- Remove the rubber insert from the spark plug type sockets to prevent contamination.
- Using an extra long 15.875 mm (5/8 in.) deep-well rubber insert spark plug socket, loosen the spark plug; turn counterclockwise.
- Do not completely remove the spark plug from the threads.
- Slip a length of 3/8 inch inside diameter hose over the plug end and continue to turn counterclockwise until threads disengage.
- Lift the spark plug out of the adapter with the hose, being careful not to drop it; mark or tag spark plugs with cylinder number.
- Visually inspect the plug wires, extenders and connections for corrosion, damage or arcing.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Source: Cummins/Onan owner'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.