Katerina Swanson
Air in the fuel system is a serious problem for diesel engines, causing a decrease in engine power, poor mileage, and even breakdowns. Air can enter the fuel system in several ways, including through a faulty gasket, a crack in the fuel hose, or a faulty fuel pump. To remove air from the fuel system, the airlock must be released by forcing fuel through and pushing the trapped air out. This is known as bleeding and can be done manually by following a specific order, usually starting with the secondary filter before moving to the injector pump and injectors. There are also products available that can help remove air from diesel fuel systems, such as the AirDog® fuel system, which can make the process easier and prevent future airlocks.
| Characteristics | Values |
|---|---|
| How air enters the system | Running out of fuel, leaks in fuel lines, faulty gaskets, faulty seals in the fuel filter, fuel pump problems, etc. |
| Symptoms of air in the system | Engine difficulty starting, reduced engine power, black smoke from the exhaust pipe, unstable idling, increased fuel consumption, etc. |
| Preventative measures | Regular maintenance, checking fuel filter, fuel hoses, seals, and pump, using quality fuel, etc. |
| Bleeding air from the system | Turn off the fuel valve, clean the filter housing, install a new filter, open the bleed plug, use a manual pump, cover venting units, etc. |
| Tools | Clean rag or towel, wrench or bleeder screw key, old fuel cap, air fitting, regulator, air compressor, etc. |
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What You'll Learn
Identify the source of the air leak
To identify the source of an air leak in your diesel fuel system, it is important to first understand how air can enter the system. Air can enter the fuel system in several ways, including running out of fuel, leaks in your fuel lines, or a faulty fuel filter.
If you suspect a leak in your diesel fuel system, there are several steps you should take to identify the source:
- Inspect the engine and familiarize yourself with the key components of the diesel fuel system, including the fuel tank, fuel lines, fuel filter, and fuel injectors.
- Check for any obvious signs of leaks or damage, such as cracks or cuts in the fuel lines or hoses.
- If no obvious leaks are detected, consider performing a leak dye test or a rail pressure bleed-off test to help identify the source of the leak.
- Pay close attention to the high-pressure fuel system, as leaks in this area can lead to serious problems, including difficulty starting the engine and low power.
- Check the fuel pump and the fuel filter for any issues, as these are common sources of air leaks. Ensure that the fuel filter is installed correctly and that the seals are securely fastened.
- Inspect the injector fuel line rail connections for any external leaks or loose lines. If leaks or loose lines are found, tighten the connections and recheck for leaks.
- If the source of the leak is still not identified, consider seeking professional assistance or consulting the vehicle's manual for further guidance.
By following these steps and performing a thorough inspection of the diesel fuel system, you can effectively identify the source of an air leak and take the necessary steps to resolve the issue.
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Check for common symptoms of an airlock
An airlock in a diesel engine occurs when air gets trapped in the fuel system, preventing the engine from starting or causing it to run poorly. Here are some common symptoms of an airlock:
- Difficulty starting the engine: Airlocks can cause difficulty starting the engine or, in severe cases, the engine may not start at all.
- Reduced engine power: Airlocks can lead to a loss of power or decreased performance. Engine power may be reduced after starting or while driving.
- Engine misfire: Airlocks can cause the engine to misfire or experience sudden stops.
- Fuel inefficiency: Airlocks can negatively impact fuel efficiency and economy, reducing the mileage of your vehicle.
- Damage to engine components: Airlocks can damage critical engine parts over time, including the fuel pump, fuel lines, and injectors.
It is important to note that airlocks can occur due to various factors, including running out of fuel, leaks in fuel lines, improper fuel filter changes, or component failures. Regular maintenance and timely replacement of worn-out parts are crucial to prevent and address airlock issues.
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Bleed air from the fuel system
Air in the fuel system can cause a variety of problems, including unstable idling, a decrease in engine power, black smoke from the exhaust pipe, and uneven engine operation at high speeds. It can also lead to fuel pump damage and additional repair costs. Therefore, it is important to bleed air from the fuel system.
Before attempting to bleed the air from the fuel system, ensure you have determined how air entered the system and address the root cause to prevent re-entry. Common causes include a faulty gasket, cracks or cuts in the fuel hose, faulty seals in the fuel filter, and problems with the fuel pump. Additionally, air can enter the system when the fuel tank runs out of fuel, during routine maintenance or replacement of the fuel filter, or through leaks in the fuel lines.
To bleed air from the fuel system, follow these steps:
- Familiarize yourself with the engine and identify the key components of its diesel fuel system, including the fuel tank, fuel lines, fuel filter, and fuel injectors.
- Turn off the engine and remove the ignition key from the cylinder.
- Locate the fuel filter and determine if it has a built-in bleeder screw.
- If the fuel filter has a bleeder screw, position a clean rag or towel underneath to catch any fuel spills. Use a wrench or bleeder screw key to slowly loosen the screw in a counterclockwise direction. A mixture of air and fuel should bleed from the screw.
- If the fuel filter lacks a bleeder screw, you may need to crack open the fuel lines on each injector and turn it over until fuel starts coming out. Then, retighten the lines.
- Cover all venting units to prevent spills.
- Locate and open the bleed plug on your secondary filter.
- Open the fuel supply valve to ensure fuel is available to the filter and pump.
- Use a manual or hand priming pump to push fuel through the system and replace trapped air. Pump several times until a full flow, without air bubbles, escapes from the bleed plug holes.
- Finally, dispose of any spilled fuel, clean up, and return your tools to their proper location.
To reduce the likelihood of having to bleed air from your fuel system in the future, consider replacing your current primary fuel filter with an AirDog® fuel system. AirDog fuel systems remove entrained air from diesel fuel and help increase mileage and injector life by removing water, vapour, and contaminants. Regular preventive maintenance, including checking the condition of fuel filters, fuel hoses, seals, and the fuel pump, is also crucial to preventing air from entering the fuel system.
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Prevent air from entering the fuel system
To prevent air from entering the fuel system, regular preventive maintenance is necessary. Here are some detailed steps to achieve this:
Firstly, it is important to regularly check the condition of the fuel filter and replace it as per the vehicle manufacturer's recommendations. When replacing the filter, ensure that it is installed correctly and that the seals are securely fastened. This is crucial because air can enter the system if the fuel filter replacement procedure is not carried out correctly.
Secondly, inspect the condition of the fuel hoses and seals for any cracks, wear, or damage. If any issues are identified, replace the affected parts immediately. Faulty gaskets, cracks or cuts in the fuel hose, and faulty seals in the fuel filter are common entry points for air to enter the system.
Thirdly, monitor the condition of the fuel pump and replace it if necessary. A faulty fuel pump may not provide enough pressure, allowing air to enter the system.
Additionally, always use high-quality fuel. Poor-quality fuel can increase the likelihood of air entering the fuel system.
Finally, adhere to the recommended regular inspection and maintenance of the entire fuel system, as outlined in the vehicle manufacturer's guidelines. This proactive approach will help maintain optimal performance and reduce the chances of air entering the fuel system.
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Clean up and dispose of spilled fuel
Diesel spills are a critical environmental issue that demands immediate attention. Diesel is toxic to marine life and can cause skin irritation and poisoning in birds and mammals that come into contact with contaminated water. It poses direct health risks to humans as well, particularly those involved in cleanup operations. Therefore, it is important to clean up and dispose of spilled diesel fuel properly.
First, stop the diesel from spilling further by, for example, putting the container that was knocked over upright or sealing the leak. Then, contain the spill with spill control equipment, such as drain plugs to stop it from going down drains, or absorbent pads to soak up the fuel. Only trained professionals wearing personal protective equipment (PPE) should attempt to contain the spill. If there are any ignition or heat sources in the area, evacuate and contact the emergency services for advice. If your staff are trained to use a diesel spill kit, they can clean it up, or you can bring in professional cleaners.
To clean up diesel fuel spills, you can use either OS Step 1 & Step 2 or OS Oil Absorbent Powder, depending on the size of the spill. For smaller spills, use the following steps:
- Control the spill at the source to avoid any further diesel being added while you are cleaning.
- Apply OS Step 1 Liquid generously to the entire area of the spill.
- Immediately apply OS Step 2 Liquid to the same area.
- Using a broom, rag, or other items, scrub the applied liquid products into the spill.
- Wash the affected area with water.
- Repeat steps 3-5 until all diesel is removed.
For larger spills, use OS Oil Absorbent Powder. Spread the powder throughout the spill with a broom to make sure all the diesel has met with the powder. Collect the combined powder and diesel and throw it out in any trash receptacle.
Dispose of the diesel and contaminated waste at licensed hazardous waste disposal sites. Coordinate with local environmental authorities to identify these sites and arrange transportation.
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Frequently asked questions
The presence of air bubbles within a diesel fuel system is known as an airlock. Airlocks commonly occur following routine maintenance to the fuel line, fuel filter replacements, or when your fuel tank runs out of fuel.
The main symptoms of air entering the diesel fuel system are unstable idling, a decrease in engine power with increasing load, the appearance of black smoke from the exhaust pipe, and uneven engine operation at high speeds.
If you are unsure whether there is a leak in your diesel fuel system, look out for the symptoms of an airlock as mentioned above. You can also keep an eye out for common symptoms such as a decrease in engine power, poor economy, and even breakdowns.
Here is a step-by-step process to get air out of your diesel fuel system:
- Turn off the fuel valve.
- Clean the outside of the filter housing.
- Install a new filter element and new gaskets.
- Open the bleed plug on the filter closest to the fuel tank.
- Open the fuel supply valve.
- Use a manual pump to prime your diesel engine by pushing fuel through your system.
