Cummins/Onan — Replace Fuel Filter (Spin-On Type)
Maintenance
From a Cummins/Onan owner's manual covering: 4B3.9, 4BT 3.9, 4BTA 3.9, 6B5.9, 6BT 5.9, 6BTA5.9, B3.9, B5.9, C8.3. Check it applies to your exact model before use.
Applies to: Cummins/Onan 4B3.9, Cummins/Onan 6BTA5.9, Cummins/Onan B5.9 engine
Before you start
- Mechanical overtightening will distort threads, filter element seal, or filter can.
Procedure
- Warn the area around the fuel filter head. Remove the filter(s).
- Clean the gasket surface of the filter head.
- Replace the o-ring.
- Fill the new filter(s) with clean fuel, and lubricate the o-ring seal with clean lubricating oil.
- Install the filter as specified by the filter manufacturer.
Tools required
- 75 to 80 mm and 90 to 95 mm filter wrenches Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
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.