Katerina Swanson
Bleeding air from a fuel line is a common maintenance task for diesel engines, especially those without an AirDog® fuel system. This process is often necessary when a diesel engine like the Grasshopper 725D runs out of fuel and needs to be bled to start again. This is because air bubbles can form in the fuel filter, causing the engine to struggle to start. To bleed air from the fuel system of a Grasshopper 725D with a Kubota D502-EF01 engine, there are several methods that can be employed, including opening the bleed screw at the injection pump, using a hand primer pump, or loosening high-pressure fuel lines.
How to bleed air from the fuel line of a Grasshopper 725D
| Characteristics | Values |
|---|---|
| Engine | Kubota D502-EF01 |
| Fuel | Diesel |
| Fuel system | AirDog® fuel system |
| Bleed air from the fuel system | Turn the key on and off several times |
| Open the bleed screw at the injection pump | |
| Loosen the high-pressure fuel lines at the cylinder head | |
| Pump fuel with a battery pump into the lines and filters while cracking open the bleeder valve | |
| Close the valve when no air is seen | |
| Preventative measures | Replace the primary fuel filter with an AirDog® fuel system |
| Change the fuel filters |
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What You'll Learn
Identify how air entered the fuel system
To identify how air entered the fuel system of a Grasshopper722, you should first check the fuel tube. Pull out the fuel tube from the tank and inspect it for any cracks or damage. If the tube is cracked, it may be sucking in air or even drawing debris from the bottom of the tank, which could lead to air bubbles in the fuel system.
Another potential cause of air in the fuel system is an airlock in the fuel filter. This can occur if the mower has been left sitting for a long period, especially in cold or wet weather conditions. To check for an airlock, you should open the bleed screw at the injection pump and use a hand primer pump to pump out any air. If there is an airlock, you will need to bleed the air out of the lines before the mower will start.
It is also possible that air entered the fuel system if the fuel tank was allowed to run completely dry. If this is the case, air may have entered the fuel lines, causing an air bubble that prevents the mower from starting. To resolve this, you will need to bleed the air out of the lines using the bleeder valve near the pump.
In some cases, the issue may be related to the fuel pump itself. If the fuel pump is not working properly, it may not be circulating fuel effectively, leading to air bubbles in the system. To check this, you can test the fuel pump to see if it is moving fuel as it should. If the fuel pump is faulty, it will need to be repaired or replaced.
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Open the bleed screw at the injection pump
To open the bleed screw at the injection pump, you must first locate the bleed screw. This can vary depending on the make and model of the injection pump. For example, on a Massey Ferguson 50B digger, there are two bleed screws on the CAV injection pump. One is on the intake side and is used when working the lift pump, and the other is further downstream on the low-pressure side, used when cranking the engine.
Once you have located the bleed screw, you will need to loosen it to open it. If it is a small screw, you may need to use a small screwdriver or other appropriate tool to loosen it. Be careful not to strip the screw head or damage the screw thread.
After opening the bleed screw, you may need to use a hand primer pump to pump out the air from the fuel line. This will help to ensure that all air is removed from the system.
It is important to note that before attempting to bleed the air from the fuel system, you should determine how air entered the system in the first place. This will help to prevent air from re-entering the system after the bleeding process. Additionally, if the fuel filter is old or nearing the end of its life, it may be a good idea to replace it during this process.
Finally, once you have opened the bleed screw and removed the air from the system, be sure to retighten the screw securely.
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Loosen high-pressure fuel lines at the cylinder head
Loosen the high-pressure fuel lines at the cylinder head by first locating the cylinder head bore. This can be found by following the high-pressure fuel line from the injection pump body to the head.
Before starting, ensure you have the proper tools for the job. It is recommended to use "hose" wrenches, which contact all six sides of the connectors and will not strip them out or slip off. It is also important to wear safety goggles when working underneath the car.
Now, follow these steps:
- Jack up the car to gain access to the underside.
- Disconnect the fuel line from underneath the car.
- Loosen the fitting at the other end of the hose in front of and above the gas tank.
- Use a 19-mm wrench on the hose "nut" and a 14-mm wrench on the metal pipe "bolt".
- The bolt rotates counterclockwise and the nut rotates clockwise, as you are laying on your back, head towards the front of the car, looking up at the fitting.
- Be sure to only loosen the fitting; it is not necessary to disconnect it.
Note: High-pressure fuel lines are one-time-use only and must be replaced once loosened or removed.
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Use a hand primer pump to pump air out
To bleed air from the fuel line of a Grasshopper 722, you can use a hand primer pump to pump air out. This can be done by first opening the bleed screw at the injection pump or the line going into the injection pump. Then, use the hand primer pump to pump out the air.
If you are experiencing issues with air in the fuel line, it is important to check all fuel line connections, the filter, and all its seals. If the primer is still soft with the engine off after a few pumps, this indicates that there is air in the system.
In some cases, the previous owner may have changed the filter, and the top O-ring that sits between the filter and the hand primer may have fallen out or not been put back in. This can cause the primer to soften over time. To fix this, you can purchase a replacement O-ring and install it.
Additionally, you can connect a clear hose between the filter and the injection pump to check for air bubbles. If you see air bubbles, this indicates that there is air in the fuel line.
By following these steps and using a hand primer pump, you can effectively bleed air from the fuel line of a Grasshopper 722.
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Replace the primary fuel filter with an AirDog® fuel system or a new filter if the old one is full
To replace the primary fuel filter with an AirDog® fuel system or a new filter, you must first determine how air entered the fuel system. This is important so that air does not re-enter the system after the bleeding process.
Before starting, ensure you have the proper supplies and that you are working in a well-ventilated area. Keep rags ready to clean up any fuel spills and have a container ready to catch any fuel or residue that may drip during the process.
First, locate the existing AirDog® water separator and fuel filter. Next, place a clean container beneath the filters to catch any dripping fuel or residue. Drain the water separator, loosen and drain the filters, and then unscrew both filters. Put a small amount of oil on the O-rings and clean up all mating surfaces.
If you are installing an AirDog® fuel system, fill the water separator with diesel before installation. Then, screw the new fuel filter into place in a clockwise direction until it is snug, being careful not to overtighten it. Turn the key to the "ON" position without starting the engine and let the AirDog® pump run for about 30 seconds. This will prime the system and ensure there are no air pockets in the fuel lines.
If you are installing a new filter, put new filters back on, ensuring you do not fill the filter with diesel to avoid introducing particles into your fuel system. Lubricate the gaskets and open the water drain valve on the new filter until diesel and no air come out; then, close the valve. Open the bleeder on the filter head, turn the key on, and let it run until no air comes out.
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Frequently asked questions
To bleed air from the fuel line of a Grasshopper 725D, follow these steps:
- Identify how air entered the fuel system to prevent it from happening again.
- Open the bleed screw at the injection pump or the line going into the injection pump.
- Use a hand primer pump to pump air out of the system.
- Close the bleeder screw and see if the engine starts.
- If it does not start, loosen the high-pressure fuel lines at the cylinder head, crank until you have fuel squirting out, tighten the lines, and try again.
Bleeding air from the fuel line can improve fuel economy, enhance performance, and reduce engine wear and tear.
To prevent air from entering the fuel system, consider installing an AirDog® fuel system, which automatically removes air from diesel fuel and is more forgiving of procedural mistakes.
If your engine is having trouble starting, particularly if it has been sitting for more than 30 minutes, it may be necessary to bleed air from the fuel line.
