Fuel Bleeding Procedure for the John Deere 350G Excavator

[MikePhua]

The John Deere 350G and Its Fuel System Architecture
The John Deere 350G LC is a full-size hydraulic excavator introduced as part of Deere’s G-series lineup, designed for heavy-duty excavation, demolition, and site development. With an operating weight of approximately 35 metric tons and powered by a 271-hp Tier 4 Final diesel engine, the 350G combines high breakout force with fuel-efficient performance. Its fuel system includes a high-pressure common rail injection setup, electronic control unit (ECU), lift pump, primary and secondary filters, and a self-priming electric fuel pump.
As with most modern diesel systems, air intrusion during filter changes, fuel line repairs, or tank drain-down can cause hard starting or complete failure to run. Bleeding the fuel system correctly is essential to restore pressure and purge trapped air from the lines and injectors.
When and Why Fuel Bleeding Is Necessary
Fuel bleeding becomes necessary under the following conditions:

• After replacing fuel filters
  
• Following fuel line disconnection or replacement
  
• After running out of fuel
  
• During injector or pump service
  
• When air bubbles are observed in the return line
  
• If the engine cranks but fails to start despite fuel in the tank
  

In Shanghai, a contractor servicing a 350G after a filter change found the machine would crank but not fire. After performing a full bleed cycle, the engine started immediately and ran smoothly.
Fuel System Components Involved in Bleeding
Key components in the bleeding process include:

• Fuel tank and supply lines
  
• Electric lift pump (mounted near the tank or frame rail)
  
• Primary fuel filter with water separator
  
• Secondary fuel filter near the engine
  
• Fuel rail and injectors
  
• Manual priming port or bleed screws (if equipped)
  
• ECU-controlled fuel pump relay
  

Unlike older mechanical systems, the 350G relies on electronic control for pump activation and timing. The lift pump is designed to self-prime, but trapped air can still prevent full pressure buildup.
Step-by-Step Bleeding Procedure
To bleed the fuel system on the John Deere 350G:

1. Turn ignition to ON without starting the engine. This activates the lift pump for approximately 30 seconds.
   
2. Wait for pump cycle to complete, then turn ignition OFF. Repeat this cycle 3–5 times to allow the pump to purge air from the filters and lines.
   
3. Inspect fuel filter housings for leaks or improperly seated seals. Tighten as needed.
   
4. Check for fuel at the secondary filter outlet. If no fuel is present, repeat ignition cycles.
   
5. Crank the engine for 10–15 seconds. If it does not start, wait 30 seconds and try again.
   
6. Monitor exhaust for white smoke, which indicates fuel is reaching the cylinders but not combusting due to air.
   
7. Continue cranking cycles until the engine fires. Once running, allow it to idle for several minutes to stabilize pressure.
   
8. Inspect return lines for bubbles. If present, continue running until they clear.
   

Some operators install a transparent section of fuel line near the secondary filter to visually confirm air purge. Others use diagnostic software to monitor fuel rail pressure during startup.
Common Pitfalls and Solutions
Issues that may prevent successful bleeding:

• Loose filter seals: Allow air to re-enter the system.
  
• Faulty lift pump relay: Prevents pump activation during ignition cycle.
  
• Clogged filters: Restrict flow and delay pressure buildup.
  
• Low battery voltage: Reduces cranking speed and pump performance.
  
• Injector leak-off: Allows air to backflow into the rail.
  

Solutions:

• Replace filters with OEM or high-quality equivalents
  
• Test lift pump relay and wiring harness
  
• Charge or replace battery before bleeding
  
• Inspect injector return lines for cracks or loose fittings
  
• Use fuel conditioner to prevent microbial growth and water contamination
  

In Alberta, a fleet manager added a manual override switch to activate the lift pump independently during bleeding. This allowed technicians to purge air without cycling the ignition repeatedly.
Preventive Measures and Maintenance Tips
To reduce the need for bleeding:

• Replace fuel filters every 500 hours or as recommended
  
• Keep tank above 25% to prevent air draw during slope work
  
• Use clean funnels and sealed containers during refueling
  
• Inspect lines and fittings during every service interval
  
• Add a pre-filter or sediment trap for dusty environments
  

Some crews install auxiliary fuel pressure gauges to monitor system health and detect early signs of restriction or air intrusion.
Field Anecdote and Practical Insight
In Baghdad, a 350G used for foundation excavation began stalling intermittently. The crew discovered that the secondary filter had been installed without lubricating the gasket, causing a slow air leak. After reinstalling the filter with proper torque and lubrication, the issue disappeared. A minor oversight had caused hours of downtime.
Conclusion
Fuel bleeding on the John Deere 350G is a critical procedure that ensures reliable engine startup and performance after service or fuel system disruption. With its electronically controlled lift pump and high-pressure injection system, the 350G requires a methodical approach to purge air and restore pressure. By following the correct steps and maintaining system integrity, operators can keep their machines running smoothly across demanding conditions and long workdays.