To remove air from a fuel filter and the fuel system, you need to perform a process called bleeding. This involves opening a specific point in the system to allow trapped air to escape while fuel flows through.
Air can enter the fuel system during maintenance, such as changing the fuel filter, or if the fuel tank runs dry. Air bubbles in the fuel can prevent the engine from starting or running smoothly.
Steps for Bleeding Air from a Fuel Filter
The process typically involves using a bleed plug and a priming pump, common on many fuel systems.
- Locate the Bleed Plug: Find the bleed plug on the fuel filter housing. This plug is usually located on the filter closest to the fuel tank.
- Open the Fuel Supply: Ensure the fuel supply valve (if present) is open so that fuel is available to flow through the system, including to the filter and pump.
- Open the Bleed Plug: Loosen or open the bleed plug. Have a rag or container ready to catch the fuel and air that will be expelled.
- Use the Priming Pump: Most equipment has a hand priming pump lever. Operate this lever repeatedly. This action pumps fuel from the tank through the filter and system, pushing air bubbles towards the open bleed plug.
- Monitor the Bleed: Continue pumping the hand primer. Initially, you will likely see fuel mixed with air bubbles or hear hissing. Keep pumping until a steady stream of bubble-free fuel flows from the open bleed plug.
- Close the Bleed Plug: Once only clean fuel is coming out, tighten the bleed plug securely. Do not overtighten.
- Test the System: Attempt to start the engine. If it starts and runs smoothly, the bleeding process was successful. If it struggles or doesn't start, you may need to repeat the bleeding process or check for air in other parts of the system (like the injection pump).
Why Bleeding is Important
- Removes air pockets that can block fuel flow.
- Ensures consistent fuel pressure for proper injection.
- Allows the engine to start and run correctly.
- Prevents potential damage to fuel injection components that rely on fuel for lubrication.
By following these steps, you can effectively remove trapped air and restore proper function to your fuel system after servicing or encountering an airlock.
