Cummins/Onan QST30 / QST30 G-Drive — Fuel Line Venting
Maintenance · Fuel System
For the Cummins/Onan QST30 / QST30 G-Drive, from the Cummins/Onan service manual.
Applies to: Cummins/Onan QST30, Cummins/Onan QST30 engine
Before you start
- The pressure of the fuel in the line is sufficient to penetrate the skin and cause serious bodily harm. Carefully loosen the fittings and wear hand protection.
- Do not engage the starter for more than 30 seconds each time when venting the system. Wait 2 minutes between engagements.
Procedure
- Low pressure lines: loosen the fuel filter head pressure relief banjo fittings (1) on top of the fuel filter head.
- Operate the plungers (2) on the fuel lift pumps until fuel flowing from the pressure relief fittings is free of air.
- Tighten the banjo fittings (1); torque 8.8 N-m [6.5 ft-lb].
- Pump(s): loosen the fuel pump galley outlet line banjo fitting(s) (3).
- Energize the Fuel Pump Shutoff Valves (24VDC) and operate the lift pump plunger, or crank the engine, until fuel bleeds from the line.
- Tighten the fuel pump galley outlet line banjo fitting(s) (3); torque 23 N-m [17 ft-lb].
- High pressure lines: loosen the fittings at the injectors; crank the engine to bleed trapped air; tighten the fittings.
- Start the engine, and after it starts vent one line at a time until the engine runs smoothly.
Tools required
- Hand protection Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Banjo fittings 8.8 N-m [6.5 ft-lb]
- Galley outlet line banjo fitting 23 N-m [17 ft-lb]
Full service-parts list: Cummins/Onan QST30 →
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.