Mercedes Mullins
The LMM Duramax is a 6.6-liter diesel V8 engine introduced by GM in 2001. While most diesel pickups have a lift pump in the fuel tank, the LMM Duramax does not. This has led to some issues with fuel delivery and has prompted some owners to install aftermarket lift pumps. There are various options for installing a lift pump, including using a FASS Titanium Signature Series 165 or an AirDog DF-165-4G lift pump kit. The installation process can vary depending on the vehicle's configuration, such as the location of the fuel tank and the available space for mounting the pump.
| Characteristics | Values |
|---|---|
| Does the LMM have a fuel lift pump in the tank | No |
| Why doesn't the LMM have a fuel lift pump in the tank | GM introduced the Silverado HD's powered by the 6.6-liter Duramax diesel V8 without a lift pump |
| How to add a lift pump to the LMM | Purchase a lift pump kit and mount the pump between the fuel tank and the engine |
| Common issues with adding a lift pump to the LMM | Limited options due to the Titan tank |
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What You'll Learn
The LMM fuel pump relay doesn't power anything
The LMM fuel pump relay may not power anything because it is not connected to anything. One source suggests that the fuel pump relay is in place due to manufacturing streamlining, allowing GM to use just one panel for both diesel and gas motors.
However, the LMM fuel pump relay can be used to power a lift pump. One user reports that they used the relay to power their lift pump.
If you are experiencing issues with your LMM fuel pump relay, there are several troubleshooting steps you can take. First, check if there is power to the fuel pump relay. This can be done by checking the fuse box and ensuring that there is power to the bottom side of the fuse box for the relay. If there is no power, try manually powering the fuse box slot by hotwiring it directly to the battery. If this does not work, you may need to replace the fuel pump relay.
Additionally, you can try using a vacuum gauge to check the suction side of the fuel system. If there is too much restriction, even after changing the filter, check for collapsing soft fuel lines. You should also check for air in the fuel system by installing clear lines before and after the filter housing. Finally, confirm the actual versus desired rail pressure, even under crank no-start conditions. If these checks do not resolve the issue, you may need to consult a mechanic or a specialist for further assistance.
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The LMM fuel pump is not electric
The LMM fuel pump is referred to as a "fuel pickup" because it draws fuel directly from the tank. This is why every diesel vehicle should have a lift pump. A lift pump is a fuel pump that sends diesel up to the fuel rail, where the diesel injection pump then ingests it, steps up the pressure, and sends it to the injectors.
Installing an electric lift pump near the tank and pushing around 10 psi of fuel to the injection pump can take a lot of stress away from the CP3 and allow it to focus on creating high-pressure fuel. The PPE Lift Pump, for example, bolts to the frame rail, intercepts the stock suction line, and pushes the fuel on its way to the engine. It is capable of pumping up to 160 gallons of fuel per hour and is compatible with biodiesel, low, and ultra-low sulfur diesel, as well as other select fuels.
The installation of a lift pump can be easy, with no modifications required, and comes equipped with wiring to just plug into your fuse box. However, some installations may require removing the truck bed or dropping the tank to access the fitting at the top of the fuel tank.
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Duramax engines don't have a lift pump
The Duramax is a 6.6-liter diesel V8 engine introduced by GM in 2001. It was the first of the big three to come equipped with common-rail fuel injection. However, unlike other diesel pickups, the Duramax engine did not have a lift pump, which is a low-pressure fuel pump that sits in or near the fuel tank and delivers fuel to the high-pressure injection pump. This pump helps to ensure that the engine has enough fuel during high-demand situations, such as when the accelerator pedal is smashed.
The absence of a lift pump in the Duramax engine has been a mystery to many, as it is a common component in other diesel pickup trucks. The Bosch CP3 and CP4 injection pumps used by GM without a lift pump were also used by Ram and Ford with a lift pump. It wasn't until 2017 that GM finally installed a lift pump on their trucks.
The Duramax engine relies on the vacuum generated by the injection pump to suck the fuel out of the tank. This system works until a component such as a hose clamp or an o-ring in the priming head deteriorates, causing the injection pump to suck air instead of fuel. This can lead to starting issues and reduced longevity for the injection pump and injectors.
Despite the absence of a lift pump, many Duramax engines have driven billions of miles without functional problems attributed to the lack of a lift pump. However, some owners have encountered issues such as losing prime and have had to spend upwards of $3000 on high-pressure fuel pump replacements.
Installing a lift pump in a Duramax engine can be done through kits such as the AirDog DF-165-4G lift pump kit or the Fleece Powerflo in-tank lift pump. These kits can improve fuel delivery, ease starting issues, and add longevity to the injection pump and injectors. However, they can also be expensive, with costs ranging from a few hundred dollars to nearly $700.
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Lift pumps can be installed in Duramax engines
The Duramax is a 6.6-liter diesel V8 engine introduced by GM in 2001. While most diesel pickups have a "lift pump", this generation of Duramax does not. Instead, it relies on the vacuum generated by the injection pump to suck the fuel out of the tank. 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.
There are a few things to consider when installing a lift pump in a Duramax engine. Firstly, access to the top of the tank may be required, which can be difficult depending on the configuration of the bed and cab. Additionally, the quality of the kit and the clarity of the instructions should be carefully considered, as poor quality control and instructions can make the installation process more challenging.
It is also important to note that while lift pumps can be installed in Duramax engines, they are not a standard feature. Some later models of the Duramax engine did eventually include a lift pump, but it is not clear exactly when this change was made.
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Lift pumps are spliced between the fuel tank and engine
A lift pump, also known as a transfer pump, is a low-pressure fuel supply pump that transfers fuel from the tank to the injection pump. It is found in many diesel vehicles. The pump is spliced between the fuel tank and the engine, with a return line that dumps unused fuel back into the tank.
Lift pumps are typically small electric motor-driven devices controlled by an electronic control module. They are considered low-pressure, high-volume pumps. There are two main types of lift pumps: mechanical and electric. Mechanical lift pumps have fixed fuel pressure and volume, while electric lift pumps have flexible fuel pressure and adjustable volume, usually controlled by an electronic fuel pump control module.
The installation process for a lift pump involves mounting the pump assembly and completing the fuel line plumbing. The pump is spliced between the fuel tank and engine, with a new line run from the top of the tank to the input of the lift pump. The output of the pump is then connected to the input of the fuel cooler, and a tee is inserted into the filler neck hose for the return line.
Some vehicles, such as the Duramax, do not come with a lift pump. However, it is possible to install one as an aftermarket modification. For example, the owner of a 2008 Chevy Duramax Diesel chose to install a lift pump to address starting issues caused by the fuel system losing its prime. Similarly, a 2016 Chevrolet Silverado with a Duramax was retrofitted with a lift pump that replaced the fuel sump and sending unit in the fuel tank.
Lift pumps are an essential component of diesel fuel systems, ensuring a steady feed of air-free fuel to the engine. They can improve engine performance, extend the service life of injection pumps and injectors, and enhance fuel efficiency by returning unused fuel to the tank.
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Frequently asked questions
No, the LMM does not have a fuel lift pump in the tank.
It is unclear why the LMM does not have a fuel lift pump in the tank, but it is speculated that it may be due to manufacturing streamlining or the use of a common fuse block for gas and diesel engines.
Yes, you can add a fuel lift pump to your LMM. There are various options available, such as the AirDog DF-165-4G lift pump kit or the FASS Titanium Signature Series 165. However, it is important to carefully consider the installation process and ensure that you have access to the necessary components, such as the fuel tank and engine, to splice the pump.
