Cummins/Onan — Spark Plug Installation
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
- Mechanical overtightening can damage the spark plug and cylinder head.
- Dirt, oil and finger prints reduce the seal strength between the spark plug boot and the porcelain.
Procedure
- Install a new spark plug in the cylinder head; make sure the insulator porcelain is clean.
- Use an extension and magnetic spark plug socket (Snap-On P.N. S971KA) and thread in by hand to make sure threads are smooth.
- Turn the plug clockwise to tighten; use a torque wrench to complete the installation.
- Torque value: 35 to 41 N.m [26 to 30 ft-lb].
- Apply a small amount of dielectric grease inside the spark plug boot and outside of the spark plug boot.
- Carefully place plug boot onto the top of the spark plug terminal; firmly press each plug boot down until a snap is felt.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Spark plug torque 35 to 41 N.m [26 to 30 ft-lb]
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.