Duramax engines are known as good and reliable engines, but they have some common issues. Duramax fuel system is prone to different problems like low fuel rail pressure, fuel injectors failures, etc. Also, often there is an air leak in the fuel system. When that happens, you need to know how to bleed air from the Duramax fuel system.
So, what is the process to bleed air from the Duramax fuel system? Purging air from the fuel system is always done after replacing the fuel filter. Next, turn the air-bleed screw that is on top of the fuel filter housing. Open the fuel supply valve so the fuel can flow. Sometimes you need to bleed the filters, the fuel pump, and all the fuel lines. When all the air is out of the system, close the bleed port screw.
Knowing and understanding how the Duramax fuel system works is very important for this process. That way, you will know how to handle this issue and what mishaps you can expect. Stay with us, and learn about the fuel system and what can cause the air to come into it.
In This Article:
Overview of Duramax Fuel System and Air in the System
Symptoms of Air in the Duramax Fuel System
How Do I Prepare to Bleed Air From the Duramax Fuel System?
Components of Your Cars’ Fuel System
How to Bleed Air from Duramax Fuel System
Common Issues You May Encounter When Bleeding the Duramax Fuel System
FAQs
Final Considerations
Overview of Duramax Fuel System and Air in the System
Most diesel fuel systems work on the same principle. There is a low-pressure pump inside the fuel tank. The stream of fuel flows from the tank to the engine. This pump puts relatively low pressure on the fuel.
Diesel is known as a dirty fuel and it needs filtering. The filter is placed between the low-pressure pump and the engine. The filter prevents fuel restrictions and needs to be replaced regularly. Dirty fuel filters will prevent fuel to move through the fuel system, so conduct timely fuel filter changes.
Water tends to condensate in the fuel tank. The temperature difference between the inside of the fuel tank and the outside frequently creates this condensation. The water separator prevents this water to mix with the fuel in the fuel lines.
From the water separator, the fuel goes into the injection pump. In the injection pumps it is pressurized and sent to the rail. Most of the fuel sent to the rail goes to the injectors. In case of deceleration, the pressure release valve opens and sends excess fuel into the fuel tank. The pressurized fuel is sent to the injectors where it is sprayed into the cylinders.
This is how the Duramax fuel system works, with only one difference. The Duramax doesn’t have a low-pressure pump in the fuel tank. The fuel is pumped with the help of the Bosch injection pump.
The air can go into the fuel system if there is a leak in it. Problems with fuel filter gaskets can also result in air in the system. Also, if any condensation in the fuel tank goes to the fuel lines, it will bring air with it.
What is Duramax Fuel System?
The fuel system is responsible for delivering enough high-pressurized fuel into the engine. All parts of the system, from the pump, and the fuel lines, to the injectors must work properly. If you notice a problem with starting the engine, or with fuel economy, you should check all the elements of this system.
See Also: How To Make Traction Bars Duramax: Boost Your Truck’s Grip
Why Air in the System Can Cause Problems?
When the fuel reaches the injector it works as a cushion. This effect allows the nozzle needle to work smoothly. If there is air in the fuel system, the needle will close forcefully which can lead to cracking. Sometimes the needle can get stuck in an open or closed position, causing it to malfunction.
Symptoms of Air in the Duramax Fuel System
Several problems can air make for the engine and the fuel system:
- The engine won’t run as smoothly as it should. The air in the fuel system can cause problems when idling and accelerating. In severe cases, it can prevent the engine from starting
- You may sense a sharp, unpleasant smell coming out of the exhaust. This happens because the fuel is not properly combusted. A lot of air in the mix makes the fuel hard to combust
- You will notice a poor fuel economy. The engine cannot use the fuel properly so it will waste it
- The engine can misfire. Diesel engines with injection systems are prone to gathering air in the same spot in the lines. That creates an airlock which results in poor acceleration and misfiring of the plugs.
How Do I Prepare to Bleed Air From the Duramax Fuel System?
The process of bleeding air from the Duramax fuel system is straightforward. It doesn’t require many tools or exceptional mechanic knowledge.
Tools You Need
For this operation, you will only need a flathead screwdriver.
Safety Precautions
There is not much chance for you to get hurt during this process. But you can use safety glasses, just to be sure.
Components of Your Cars’ Fuel System
Every diesel car has 5 basic components of the fuel system, and they are:
- The fuel tank. It needs to have an adequate capacity for everyday use. It needs to be sealed off, so it cannot be contaminated. Every tank has three openings: one to receive fuel, another for discharging fuel, and one for drainage. Fuel tanks also have air vents so the air can come in to replace the fuel that is used
- The fuel lines. Depending on the fuel pressure, there are three types of fuel lines. High pressure between the fuel pump and the injectors demands heavyweight fuel lines. The second group with lower pressure can use medium-weight fuel lines. Lightweight fuel lines can support systems with little to no pressure
- Fuel filters. The dirt and foreign particles don’t belong in the fuel system. They are blocked by the fuel filters. There are three filters: the primary and the secondary filter, and the filter screen near the fuel transfer tank
- Fuel pumps. They automatically supply the injection system with fuel. If you installed a lift pump in your truck’s fuel system, then bleeding the air is simple. You only need to prime the lift pump and turn the engine on
- Fuel injectors. They supply the injectors with pressurized fuel.
Check Out Fuel System Components and Functions:
How to Bleed Air from Duramax Fuel System
Bleeding the air from a Duramax fuel system is easy when compared to some other engines. The Duramax engine has only one bleeding screw. Other engines usually have several screws and you need to bleed air at all of them.
The common problem with the Duramax fuel system is the bleeding screw. If you repeat the bleed cycles often, the plastic screw tends to fail. We always recommend changing the stock bleeding screw with a better durable aluminum screw.
Step-by-Step Guide to Bleeding the System
- Find the bleeding screw. In almost all Duramax engines, it is located on the top of the fuel filter canister housing
- Pump up the primer pump until it becomes hard. That way, you primed the fuel system
- Unscrew the bleeding screw. Don’t overdo it; it only has to be loose
- If there is any air in the system, you will hear it come out from below the bleeding screw.
Common Issues You May Encounter When Bleeding the Duramax Fuel System
The air can come into the fuel system for several reasons. Usually, it happens because there is a leak in the fuel system. The second thing that can cause problems are vapors coming from the fuel tank. Any condensation that goes from the fuel tank to the fuel lines can bring air with it. Also, there are problems with fuel filter gaskets. If they are not returned properly to the fuel filter, the air can come into the system.
FAQs
How can you prime a 6.6 Duramax’s fuel system?
You will need to prime the system if you change the fuel pump, fuel filter, injectors, or cylinder heads. Basically, every time you change any major part of the fuel system, you will need to prime it.
Every Duramax has a priming pump. It is located on the passenger side of the engine, right on top of the fuel filter assembly. Press the priming pump until it becomes hard. The system is primed, and you can unscrew the bleeding screw.
How does one prime a diesel engine without primer?
For this operation, you will need some tools:
– A wrench to remove the fuel return line before the pressure regulator
– Some type of vacuum device, or a suction gun
– A little tube with a fitting that is going to connect the fuel return line
The process is simple and straightforward.
1. Remove the fuel line before the pressure regulator
2. Hook it up to the suction gun and turn it on
3. Wait for the suction gun reservoir to be about half full
4. Turn the suction gun off and let it pull all the air out of the system
5. Hook up the fuel line like it was.
What happens if there is air in the diesel fuel line?
The engine will have lower performance, and it can have trouble starting. Also, you may experience the misfiring of the spark plugs.
Final Considerations
Not a lot of people are familiar with the problems that air in the fuel system can cause. Fuel leaks and condensation in the fuel tank can cause these problems. Also, a problem with the oil filter gasket can result in the air coming into the fuel system. Then you need to prime and bleed out the system.
Thankfully, on Duramax engines, it is a really simple process. It includes pumping the primer pump and releasing the air through the bleeding screw.
Keep your fuel system well-maintained. Replace the fuel filter regularly and check how the pump and injectors work. Also, use quality and suitable fuel because diesel can be dirty.
