Kubota standby generator shuts down during run and displays E04, will restart but trips again after a short period.

Safety first: Open the main breaker to isolate the generator from the building load before troubleshooting. Disable auto-start and disconnect battery negative if working near moving parts.

• Reduce load: With the generator running, verify that the total connected load does not exceed the generator's rated kW. Turn off large loads (HVAC, water heaters) and see if the fault clears.
• Check fuel supply: Inspect the diesel fuel level in the tank. Open the fuel shutoff valve fully. Replace the Kubota primary and secondary fuel filters if they are old or contaminated. Bleed air from the fuel system using the manual priming pump and bleed screws on the injection pump.
• Inspect air filter: Remove the air filter element and check for heavy dirt or oil saturation. Replace with a genuine Kubota air filter if restricted.
• Governor linkage: Observe the governor actuator and throttle linkage while the engine runs. Ensure there is no binding and that the actuator responds quickly to load changes. Lubricate linkage lightly.
• Frequency check: Use a multimeter with frequency function at the generator output. If frequency remains low even at no load, the governor may need calibration by a technician.