Cummins/Onan — Prime Lubrication System
Maintenance
From a Cummins/Onan service manual covering: 275 DFBF, 300 DFCB, 350 DFCC. Check it applies to your exact model before use.
Applies to: Cummins/Onan 275 DFBF, Cummins/Onan 300 DFCB, Cummins/Onan 350 DFCC, Cummins/Onan NT-855-G6 engine, Cummins/Onan NTA-855-G2 engine, Cummins/Onan NTA855-G3 engine
Parts for this job
- 123457 Oil filter — Cummins/Onan 275 DFBF Amazon eBay $17.99
- 122-0755 Oil filter — Cummins/Onan 350 DFCC Amazon eBay
Part numbers from the service-parts lists for Cummins/Onan 275 DFBF, Cummins/Onan 350 DFCC. Verify against your serial number before ordering; some links are affiliate links.
Procedure
- Remove oil inlet line from turbocharger housing; fill bearing housing with clean engine oil; reconnect line.
- Fill crankcase to L (low) mark on dipstick.
- Remove plug from head of oil filter housing.
- Connect hand or motor driven priming pump with pressure gauge to plug boss in filter housing.
- Prime until 30 psi (207 kPa) pressure is obtained.
- Disconnect wire from fuel solenoid valve.
- Crank engine while maintaining 15 psi (103 kPa) priming pressure for 15 seconds.
- Stop cranking, remove priming equipment, reinstall plug and torque to 15 to 20 ft lb (20 to 27 N•m), reconnect fuel solenoid wire and fill oil to H mark.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 30 psi (207 kPa) priming pressure
- 15 psi (103 kPa) while cranking for 15 seconds
- 15 to 20 ft lb (20 to 27 N•m) filter housing plug
Full service-parts list: Cummins/Onan 275 DFBF →, Cummins/Onan 350 DFCC →
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.