Changing The Lift Pump On A Gmc Duramax Diesel

If you're looking to change the lift fuel pump on your GMC Duramax Diesel, you're probably already aware that this generation of Duramax doesn't have a lift pump, instead relying on the vacuum generated by the injection pump to suck the fuel out of the tank. However, this can cause issues when a hose clamp no longer seals a rubber fuel hose, or an o-ring in the priming head deteriorates, causing the injection pump to suck air instead of fuel.

To fix this, you can install an aftermarket lift pump, which will not only ease starting issues but also add longevity to the expensive injection pump and injectors. There are a few options to choose from when it comes to lift pumps, ranging from simple and cheap to more complex and expensive.

If you're just looking for a basic lift pump, you can purchase a reasonably-priced helper fuel pump and splice it into the existing fuel line. However, be aware that these cheaper pumps may not last long and could cause further downtime if they fail.

For a more complete solution, you can purchase a lift pump kit, such as the AirDog DF-165-4G, which includes all the necessary mounting hardware, fuel lines, and quick-connect fittings for installation. These kits also typically include added fuel filtration and a water separator to protect your diesel hardware in case you get a load of bad fuel. While these kits are more expensive, costing around $700, they offer better reliability and peace of mind.

When installing a lift pump, whether it's a basic pump or a kit, be prepared for some challenges. You'll need to disconnect the quick-connect fittings on the fuel lines, which can be difficult to access and may require some creative problem-solving. Additionally, pay close attention to the brake lines and other existing fuel lines to avoid any interference or damage during the installation process.

Overall, adding a lift pump to your GMC Duramax Diesel can improve fuel delivery and extend the life of your injectors, but be prepared for some work and potential challenges during the installation process.

Fuel filter and water separator kit

The fuel filter and water separator kit is an important component of the fuel system in the GMC Duramax Diesel engine. It is designed to screen out contaminants such as dirt, rust, and other particles from the fuel before it enters the engine. This is crucial because these contaminants can cause rapid wear and even failure of the fuel pump and injectors. Therefore, regular replacement of the fuel filter and water separator is necessary to maintain optimal engine performance and fuel efficiency.

Compatibility

The fuel filter and water separator kit is compatible with various Chevrolet and GMC models equipped with the 6.6L Duramax Diesel engine. This includes the Chevrolet Silverado 2500 HD, 3500 HD, and 3500 Classic, as well as the GMC Sierra 2500 HD and 3500 HD, among others. It is important to refer to the specific vehicle compatibility list to ensure the correct application.

Installation

The installation process for the fuel filter and water separator kit involves several steps and requires some mechanical knowledge. Here is a general overview of the installation procedure:

• Depressurize and drain the fuel from the existing filters.
• Remove the cover on the wheel well to access the fuel filters, which are located underneath the vehicle, next to the front passenger tire.
• Disconnect the water-in-fuel sensor electrical connector and carefully remove the old fuel filter, ensuring that the sensor wire does not become entangled.
• Drain and dispose of the old fuel filter properly.
• Clean and inspect the fuel filter housing, ensuring that the gasket is in good condition.
• Install the new fuel filter with a new o-ring, lubricating it with clean engine oil. Do not overtighten.
• Bleed the fuel system by opening the bleed valve and repeatedly pumping the plunger on the fuel filter housing until diesel fuel flows out. Then close the bleed screw.
• Reinstall any components that were removed for access, such as the inner fender and intake tube.
• Start the engine and check for leaks. If the engine runs rough, turn it off, re-bleed the system, and check for leaks again.

Maintenance Interval

For GMC Duramax Diesel engines from 2001 to 2010 model years, GM recommends replacing the fuel filter and draining the fuel water separator every 15,000 miles. For 2011 to 2016 model years, the recommended interval is 22,500 miles or as prompted by the instrument cluster display. However, it is always a good idea to refer to the specific maintenance schedule for your vehicle and adjust the interval based on your driving conditions and fuel quality.

Fuel sending unit

The fuel sending unit in a GMC Duramax diesel is responsible for monitoring the fuel level and sending that information to the fuel gauge. It is located inside the fuel tank and can be accessed by dropping the tank or removing the bed of the truck. When replacing the fuel sending unit, it is recommended to also change the fuel pump and locking ring at the same time.

There are aftermarket options available for the fuel sending unit, such as the SureFlo® Performance Sending Unit, which is designed to work with aftermarket lift pumps and fits directly into the stock sending unit location. It features factory-style quick disconnects for the fuel lines, heavy-duty billet aluminum caps, and universal -8 AN ports for custom fuel setups.

Some GMC Duramax diesel owners have reported issues with the fuel sending unit, such as rotting and leaking, which can lead to air in the fuel lines and inaccurate fuel gauge readings. It is recommended to inspect the fuel sending unit and its components regularly to ensure proper functioning and prevent potential issues.

When working on the fuel sending unit, it is important to have the correct tools, such as the fuel line disconnect tool, which is required to release the fuel lines from the tank. Additionally, when dealing with fuel, ensure proper safety precautions are taken to avoid any accidents or injuries.

Fuel line modifications

The fuel lines around the cooler are prone to rusting and leaking. If you are installing a lift pump, it is a good time to replace the fuel lines. The supply line is 1/2" and the return line is 3/8".

The AirDog DF-165-4G lift pump kit is a good choice for a lift pump. The kit includes all the mounting hardware, fuel lines, and quick-connect fittings needed for installation. The pump runs at around 10 psi and costs around $700.

The installation process involves first assembling the pump and the mounting bracket. The pump should be mounted on the driver's side frame rail, with the fuel outlet facing the engine. The inner bracket needs to be slid between the frame rail and the brake line, and care must be taken not to pinch the brake line. The assembly should be mounted as high as possible to maximize ground clearance.

The next step is to connect the fuel lines. The quick-connect fittings on the fuel tank and fuel cooler need to be disconnected. A 1/2" fuel line disconnect tool can be used to press in and release the recessed clip on the quick-connect lines. The barbed ends of the new quick-connect fuel line fittings should be coated with oil before pressing the fuel line onto them.

Finally, the electrical installation of the lift pump is straightforward. The wiring harness, relay, and fuse should be connected to the battery and fuse block.

Other options for lift pumps include the FASS Titanium Signature Series and the AirDog II-4G, which offer enhanced fuel filtration and can support higher horsepower. The FASS Dura-Max Flow Enhancer is a simpler and more cost-effective option that installs a pump inline into the existing fuel system.

It is also recommended to upgrade the fuel filter to a Caterpillar 1R-0750 fuel filter, which offers better filtration down to 2 microns.

Fuel system anatomy

The fuel system in a car is designed to supply fuel from the fuel tank to the engine cylinders in a timely manner. The system also provides fuel storage and cleaning before the fuel enters the cylinders.

The basic fuel system consists of the following main elements:

Fuel Tank

The fuel tank stores the fuel and includes other elements such as the reservoir, fuel neck, fuel gauge, and fuel pump.

Fuel Pipeline System

This system of pipelines delivers fuel from the tank to other fuel system components.

Fuel Pump

The fuel pump is responsible for pumping fuel from the tank to the engine. In modern injection systems, the fuel pump creates high pressure. Diesel engine pumps can be of two types: low and high pressure. Typically, high-pressure pumps are used in diesel engines.

Fuel Filter

There are two types of fuel filters: coarse and fine. The purpose of these filters is to clean the fuel by removing dirt, dust, and other contaminants.

Fuel Injection Device or Carburetor

This device supplies a mixture of fuel and air to the engine. In diesel engines, the fuel injectors deliver fuel directly into the cylinders.

Fuel Injection System

The fuel injection system consists of electronically controlled fuel injectors that deliver the precise amount of fuel at the correct pressure and timing. The engine management system controls the fuel pressure, injector timing, and other parameters to ensure efficient engine operation and reduce exhaust emissions.

In addition to these basic components, there may be additional elements in the fuel system, such as a fuel sending unit, fuel sump, or auxiliary (aux) fuel filters and lift pumps. These components enhance the fuel delivery system and improve engine performance.

Fuel filter and water separator

The fuel filter and water separator are essential components of a diesel fuel system. They work to remove dirt, water, and other contaminants from the fuel before it reaches the injection pump and injectors. This is particularly important for the Duramax engine, as it relies on the injection pump to suck fuel from the tank, which can lead to issues with fuel delivery if the fuel is contaminated.

When choosing a fuel filter and water separator, it is important to consider the micron rating, which indicates the size of particles that the filter can remove. A lower micron rating means that the filter can remove smaller particles, resulting in cleaner fuel. For the Duramax engine, it is recommended to use a fuel filter with a rating of 2 to 4 microns.

There are several options available for fuel filters and water separators for the Duramax engine. One popular option is the Caterpillar 1R-0750 fuel filter, which has a 2-micron rating and can be installed using an adapter kit from Sinister Diesel. Another option is the FASS Titanium Signature Series pump, which includes a high-efficiency fuel filter that removes particles down to 2 microns and a water separator that removes 99.96% of water from the fuel. The FASS system also features a unique design that eliminates air from the fuel, resulting in smoother idle, longer injector and pump life, and improved emissions output.

When installing a fuel filter and water separator, it is important to follow the manufacturer's instructions and ensure that all components are securely connected. It is also crucial to change the fuel filter at regular intervals, as a clogged fuel filter can lead to a loss of rail pressure and poor engine performance. For the Duramax engine, it is recommended to change the fuel filter every 10,000 miles.

Frequently asked questions