How to John Deere 855 doesn’t start
John Deere 855 955 756 856 Tractor Service Manual
It sounds like your John Deere 855 diesel tractor is cranking well but not running, which suggests a fuel delivery or combustion issue. Here are some simple checks and steps to help you diagnose and repair the problem:
1. Check the Fuel System
a. Bleed the Fuel System
Diesel engines are very sensitive to air in the fuel lines. After sitting for two years, air might have entered the system.
- Locate the fuel bleed screw near the fuel filter or injection pump.
- Loosen the screw and manually pump the primer until fuel flows steadily without air bubbles.
- Tighten the bleed screw and try starting the engine again.
b. Inspect the Fuel Filter
- Remove the fuel filter and check for debris or water contamination.
- Replace the filter if it appears dirty or clogged.
- Fill the new filter with fresh diesel before installing it to minimize air entry.
c. Ensure Fuel Flow
- Check if fuel flows freely from the tank to the filter by disconnecting the line at the filter inlet.
- If flow is weak, check for blockages in the fuel line or tank outlet.
- Clean the fuel tank and lines if necessary.
2. Check the Air Intake System
A restricted air supply can cause rough starts or prevent the engine from running.
- Remove and inspect the air filter. Replace it if it’s dirty or clogged.
- Ensure there are no obstructions (e.g., nests or debris) in the air intake or breather tube.
3. Inspect the Glow Plug System
Glow plugs are essential for starting diesel engines in cold conditions or after long periods of inactivity.
- Turn the key to the preheat position and confirm the glow plug indicator lights up.
- If you suspect faulty glow plugs, test them with a multimeter for continuity. Replace any that are not functioning.
4. Check the Injection Pump and Injectors
If the tractor smokes black but does not run, it’s likely that fuel is reaching the combustion chamber, but not at the proper pressure or timing.
- Add a diesel injector cleaner to the fuel tank and crank the engine several times to help clear the injectors.
- If the problem persists, consider removing the injectors and having them tested or cleaned by a professional.
5. Additional Simple Checks
- Inspect the Fuel Shutoff Solenoid: Ensure the solenoid is engaging when the key is turned on. If it’s stuck or faulty, it could block fuel delivery.
- Check Compression: Low compression due to stuck rings or valve issues after long storage can also cause this issue, though this is less common.
Steps for Repair
- Bleed the fuel system to remove air.
- Replace the fuel filter and ensure fuel lines are clean.
- Inspect and replace the air filter if necessary.
- Test and replace faulty glow plugs or check the preheat system.
- Use diesel injector cleaner and ensure injectors are functioning.
If these steps do not resolve the issue, consider consulting the John Deere 855 service manual or a professional technician for more advanced diagnostics, such as timing adjustments or injector testing.
John Deere 855 955 756 856 Tractor Service Manual
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