Cummins/Onan — Clean or Replace Spark Plugs
Maintenance
From a Cummins/Onan operator's manual covering: G-1710, G-495, G-743, G-855, GTA-1710, GTA-743, GTA-855. Check it applies to your exact model before use.
Applies to: Cummins/Onan G-855
Before you start
- Spark plug adapter part #173416 requires .125 inch gasket-spacer for proper positioning of 3/4 inch reach spark plug.
Procedure
- Disconnect spark plug wire at coil.
- Lift off blue rubber cap with extension.
- Remove spark plug with extra long 13/16 inch deep-well rubber insert socket.
- Check spark plug gap; should be 0.020-0.025 inches.
- Inspect seating area in adapter and clean.
- Position new gasket; insert plug; tighten to 28-30 ft-lb torque.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- gap 0.020-0 FridayParts $214.68.025 inches
- plug torque 28-30 Amazon eBay ft-lb
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.