Cummins/Onan GTA38 / GTA50 — Sparkplug Removal
Maintenance · Ignition system
For the Cummins/Onan GTA38 / GTA50, from the Cummins/Onan owner's manual.
Applies to: Cummins/Onan GTA38 engine, Cummins/Onan GTA50 engine
Procedure
- Disconnect wire from ignition coil end first, then from sparkplug end.
- Remove rubber insert from sparkplug socket to prevent contamination.
- Use 15.875 mm (5/8 in) deep-well rubber insert sparkplug socket to loosen plug.
- Continue turning counterclockwise until threads disengage.
- Lift sparkplug out of adapter without dropping it.
- Mark or tag each sparkplug with its cylinder number.
- Inspect plug wires, extenders and connections for corrosion or arcing.
Tools required
- 5/8 in deep-well sparkplug socket Amazon
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.