Cummins/Onan — Adjust Injectors and Valves
Adjustments
From a Cummins/Onan service manual covering: V12 Series, V6-140, V6-200, V6-VAL, V6-VIM, V8-185, V8-265, V8-350, V8-VALE, V8-VINE, VT12, VT8-430. Check it applies to your exact model before use.
Applies to: Cummins/Onan V12 Series
Before you start
- Injectors must always be adjusted before valves.
- Be careful not to bruise injector tip.
Procedure
- If used, pull compression release lever back and block open.
- Bar engine in direction of rotation until No. 1 VS mark appears.
- Adjust injector plunger, then crossheads and valves of first cylinder.
- Turn crankshaft to next VS mark per firing order; adjust that cylinder.
- Continue until all injectors and valves are adjusted.
- Injector plungers adjusted with inch-pound torque wrench to torque setting.
- Warm engine to 140°F oil temperature and reset injectors to warm setting.
- Always make final valve adjustment after injectors and with engine at operating temperature.
Tools required
- Inch-pound torque wrench (Snap-On Model TQ12B or equivalent) Amazon
- Screwdriver adapter Amazon
- Feeler gauge Amazon
- Wire gauge Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Crosshead lock-nut 25/30 foot-pounds
- Crosshead-to-retainer clearance minimum .025 inch
- Two complete crankshaft revolutions needed to set all plungers and valves
Full service-parts list: Cummins/Onan V12 Series →
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.