Cummins/Onan — Priming Lubricating System - First Time

Maintenance

From a Cummins/Onan owner's manual covering: G 12, G28, G855, GTA12, GTA19, GTA28, GTA855. Check it applies to your exact model before use.

Applies to: Cummins/Onan G 12, Cummins/Onan G&855, Cummins/Onan GTA855

Procedure

1. On turbocharged engines, remove oil inlet line from turbocharger and add 50 to 60 cc (2 to 3 oz.) clean oil to prelubricate bearing; reconnect supply line.
2. Fill the crankcase to the L (low) mark on the dipstick.
3. Remove the plug from the lubricating oil crossover passage (G855/GTA855), from the oil filter housing (GTA28), or from the front of the oil cooler housing (GTA19).
4. Connect a hand or motor-driven priming pump line from a source of clean lubricating oil to the plug boss in the housing.
5. Prime until a 207 kPa [30 psi] minimum pressure is obtained.
6. Check the oil reservoir on the oil lubricator if equipped with an air-gas starter.
7. Crank the engine at least 15 seconds with the ignition OFF while maintaining external oil pressure at a minimum of 103 kPa [15 psi].
8. Remove the external oil supply and replace the plug. Tighten to the proper torque value.
9. Fill the crankcase to the H (high) mark on the dipstick with oil meeting Section 17 specifications.

Full service-parts list: Cummins/Onan G 12 →, Cummins/Onan G&855 →

Source: Cummins/Onan owner's 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.

More Cummins/Onan repair guides →