Cummins/Onan — Tappet Adjustment
Adjustments · Valve tappets
From a Cummins/Onan service manual covering: P216, P218, P220, P248. Check it applies to your exact model before use.
Applies to: Cummins/Onan P216, Cummins/Onan P218, Cummins/Onan P220, Cummins/Onan P248
Procedure
- Remove the ignition key to prevent accidental starting.
- Remove all parts necessary to gain access to the valve tappets.
- Remove the spark plugs to ease turning the engine over by hand.
- Rotate the crankshaft clockwise until the right intake valve opens and closes.
- Continue turning until the flywheel timing mark lines up with the governor shaft on the gear cover.
- Verify the left intake and exhaust valves are closed and there is no pressure on the valve lifters.
- Check that the correct feeler gauge passes freely between valve cap and tappet; a 0.002 inch thicker gauge should not.
- Turn the adjusting screw with a 7/16-inch open end wrench to obtain correct clearance; hold the tappet with a 9/16 inch (14 mm) wrench.
- For the left cylinder, turn the engine one complete revolution, line up the timing marks, and repeat.
- Replace all removed parts, tighten all screws securely, and torque valve cover bolts to specification.
Tools required
- feeler gauge Amazon
- 7/16-inch open end wrench Amazon
- 9/16 inch (14 mm) open end wrench Amazon
- torque wrench Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Intake valve clearance (cold) 0.005 in (0.13 mm)
- Exhaust valve clearance (cold) 0.013 in (0.33 mm)
Full service-parts list: Cummins/Onan P216 →, Cummins/Onan P218 →, Cummins/Onan P220 →, Cummins/Onan P248 →
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.