Fix the GSX “engine is not running” message with checks for engine state, fuel controls, controller bindings, Couatl and aircraft compatibility.
GSX shows “engine is not running” when it cannot detect a required main engine in stable combustion. If the current GSX stage expects an engine start, start the main engine—not the APU—move its fuel or condition control out of cutoff, wait for stable idle, then retry. If it is already running, refresh GSX and check bindings.
In Microsoft Flight Simulator 2020 and 2024, GSX Pro obtains this state from the engine data reported to the simulator. The legacy GSX versions for FSX and Prepar3D follow the same basic principle. A turning fan or propeller does not necessarily mean that combustion has started.
How do I clear the GSX engine-not-running message?
- Confirm what GSX is waiting for. During pushback, wait until GSX permits engine start. Boarding, catering and refuelling normally require the engines to remain off; if the warning appears during one of those services, cancel the incorrect or stale operation rather than starting an engine beside the ground crew.
- Start a main engine, not the APU. Follow the aircraft checklist and move the fuel control, condition lever or mixture out of cutoff at the correct point. Our guide to the right start sequence for piston, turboprop and jet engines covers the differences. If the message identifies an engine number, start that specific engine.
- Wait for stable idle. Check for normal RPM or N1/N2, an exhaust-temperature rise, fuel flow and oil pressure. Starter rotation, windmilling and an illuminated start switch are not proof that the engine is running.
- Check fuel and ignition controls. Verify the selected tank contains fuel, the required pumps and valves are open, ignition is configured correctly and no simulated failure is active. If the engine lights and then dies, use these fuel, ignition, failure and controller checks before blaming GSX.
- Look for duplicate controller assignments. Move each physical throttle, mixture or condition control once while watching the virtual cockpit. A second quadrant, switch panel or unused axis can repeatedly send cutoff, mixture-lean, starter or fuel-valve commands.
- Refresh GSX safely. Cancel the active service if possible, close and reopen the GSX menu, then request the operation again. If the state remains stuck, use the Couatl restart or reload option provided by the installation. Restarting Couatl ends the active GSX operation.
- Test another aircraft. Repeat the same GSX action with a default or known-compatible aircraft. If that aircraft is recognised, update the affected add-on and GSX; if every aircraft fails, concentrate on Couatl or the GSX installation.
Why does GSX think the engine is off when it is running?
If the cockpit shows a stable engine but GSX still reports it as stopped, the symptom usually identifies where the fault lies.
| What you see | Likely cause | What to do |
|---|---|---|
| Fan or propeller turning, but no temperature rise or fuel flow | Starter rotation or windmilling without combustion | Complete the fuel and ignition steps, then wait for idle |
| Engine starts and immediately returns to cutoff | Fuel starvation, a failure or a duplicate hardware binding | Check tanks, pumps, fuel controls and assignments |
| Stable engine; only one aircraft or variant is affected | The aircraft uses custom engine logic or has an integration mismatch | Update both products and test the exact aircraft variant again |
| No aircraft is recognised | Couatl is stale, stopped or damaged | Restart Couatl, restart the simulator and then run the GSX update or repair function |
Editing door coordinates or vehicle positions in a GSX aircraft profile will not correct engine-combustion reporting. Those settings solve alignment problems, not an engine-state mismatch.
Does the APU count as a running engine in GSX?
No. The auxiliary power unit can supply electrical power and bleed air for starting, but GSX does not treat it as a propulsion engine. Ground power, a spinning starter and electrically powered cockpit displays also do not satisfy an engine-running check.
What if the message appears during GSX pushback?
During GSX pushback, timing is often the problem: leave the engines off until start clearance, start them using the aircraft checklist, and wait for stable idle before confirming the next stage. Do not release the parking brake or remove chocks except when instructed.
If the tow will not begin or continue, work through the separate brake, chock and cockpit-confirmation checks; those conditions can block pushback even after GSX recognises the engine.
When should I repair or reinstall GSX?
Repair GSX only after the warning affects several aircraft and survives a Couatl and simulator restart. Run the update or repair function offered by the GSX installer, preserve any custom aircraft profiles, and retest before performing a full reinstall.
For Microsoft Flight Simulator 2024, follow our GSX aircraft-state, installation and Couatl checks if other services or the toolbar menu are also failing. When the problem affects only one aircraft, reinstalling all of GSX is unlikely to help; the aircraft’s engine-state integration is the more probable cause.