Cummins/Onan — Priming Lubricating System
Maintenance
From a Cummins/Onan service manual covering: GNH-250, GNH-XI0, GNHC4, GNVH450, GV12, GV12 series, GV12-525. Check it applies to your exact model before use.
Applies to: Cummins/Onan GV12
Before you start
- After engine runs, add oil to compensate for filter and oil cooler absorption.
Procedure
- Fill crankcase to L mark on dipstick.
- Remove pipe plug from oil filter head (GV12) or oil pump (GNH).
- Connect priming pump line to oil plug boss.
- Prime until 30 psi minimum pressure.
- Crank engine with ignition OFF at least 15 seconds, maintaining 15 psi minimum.
- Remove external oil supply and replace plug.
- Fill crankcase to H mark with specified oil.
- Check oil level after running; add oil as needed.
Tools required
- priming pump Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 30 psi minimum
- 15 psi minimum
Full service-parts list: Cummins/Onan GV12 →
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.