Cummins/Onan — Oil Pressure Relief Valve Adjustment
Adjustments
From a Cummins/Onan service manual covering: 4CCK, 5CCK, 5CCK-150R, 5CCK-3CR. Check it applies to your exact model before use.
Applies to: Cummins/Onan 4CCK, Cummins/Onan 5CCK, Cummins/Onan CCK engine
Before you start
- Low oil pressure may indicate worn main or connecting rod bearings, weak or broken by-pass spring, improperly adjusted by-pass, or a defective gage
Procedure
- Run engine until thoroughly warmed up.
- Loosen the locknut on the slotted stud near the breather tube.
- Turn stud inward to increase oil pressure, outward to decrease.
- Tighten the locknut securely after adjustment.
Tools required
- Wrench Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Oil pressure 20 to 35 lbs when engine is thoroughly warmed up
Full service-parts list: Cummins/Onan 4CCK →, Cummins/Onan 5CCK →
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.