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In diesel engines, the low-pressure fuel pump is generally called a lift pump to identify it as a different part from a high-pressure injection pump. In other words, fuel pump is the general term to describe a high-pressure injection pump, while lift pump is used to describe a low-pressure pump.
A lift pump might also be called a transfer pump or a fuel supply pump. The reason for these names is that they transfer fuel from the tank to the injection pump. Lift pumps are found in many types of diesel vehicles.
What is a Lift Pump?
There are two types of lift pumps: electric and mechanical. Most late-model diesel engines have lift pumps driven by an electric motor and controlled by an electronic control module. The benefit of an electric lift pump is flexible fuel pressure and adjustable volume. Mechanical pumps have fixed pressure and volume.
A diesel engine’s lift pump uses low pressure to move fuel from the storage tank to the next step in the fuel system.
Lift pumps are low-pressure, high-volume pumps. Conversely, a fuel pump is considered a low-volume, high-pressure pump, which is why it’s also called a high-pressure injection pump.
The location of the lift pump on a specific engine depends on which engine you’re referring to. Common locations include the back of the fuel filter housing, on the side of the block, or just above the starter motor. Most modern diesel engines have two pumps distributing fuel: the fuel pump and the lift pump. These are completely different parts.
What is a Fuel Pump?
As mentioned above, a fuel pump refers to the high-pressure pump located in the fuel tank. Diesel engines have two pumps to maintain rail pressure. The high-pressure pump takes the fuel and pressurizes it to a very high pressure. The pump then delivers the fuel to the common rail and injectors.
The main difference between high-pressure and low-pressure pumps is volume. Low-pressure pumps typically deliver much more volume than high-pressure pumps.
The fuel pump may be located in different places depending on the engine. On a Powerstroke, the high-pressure pump is near the engine and fuel lines. On a Duramax, it is likely behind the water pump.
Do All Diesel Trucks Have a Lift Pump?
Almost all diesel engines have a lift pump, whether it’s an old mechanical injection system or the newer common-rail system. One exception is the Duramax diesel engines made between 2001 and 2016.
On the inside of both the CP3 and CP4 pumps is a separate gear pump feeding fuel into the high-pressure section. However, the gear pump also creates suction that pulls the fuel from the tank, acting as a lift pump.
CP4 Pumps
If your engine already has a lift pump, you might wonder where an aftermarket lift pump comes in. The main purpose of aftermarket lift pumps is to increase engine power beyond factory settings.
This can be done with programming and/or mechanical means. Once the engine’s fuel demand is notched up, the factory lift pump is usually the first thing to fall short.
When modifying a diesel engine to increase its power and performance, it’s usually a good idea to upgrade the lift pump as well.
Common Issues and Maintenance for Lift Pumps in Diesel Trucks
The other reason you may need to replace your lift pump is if it begins to have issues. Some signs of a failing lift pump include sputtering, hesitation, stalling, reduced power, hard starts, and engine misfires.
Starting issues and performance problems are common signs that the lift pump isn’t working properly in the fuel system.
You may get a diagnostic code that identifies the lift pump as the culprit behind the above symptoms, but there are some other ways to check. Turn the key to the on position and listen at the fuel tank for a buzzing sound that means the lift pump is starting.
If you don’t hear anything, it could mean it’s not working. You can also check the fuel pressure by installing a fuel pressure gauge and comparing the readings to the manufacturer’s specifications.
Source: Duramax Forum
Replacing a faulty lift pump or fuel pump depends on your specific engine and where it’s located. It’s best to consult your vehicle’s service manual. The longevity of a lift pump varies widely.
Some factory pumps can last for 100,000 miles, while some poor-quality aftermarket pumps only last a few years. It also depends on whether you’re getting more power out of your engine and using an inadequate lift pump.
When and Why You Might Upgrade to an Aftermarket Lift Pump
As mentioned above, upgrading your lift pump whenever you decide to add more power is a good idea. An aftermarket lift pump is a good upgrade if you’re adding power or if your factory pump is failing.
If you plan to upgrade your injectors or injector pump, you should also get a new lift pump. Aftermarket lift pumps deliver higher flow rates and can supply larger injectors and modified injection pumps.
Engine modifications aren’t the only reason to get a new lift pump. A great example is the 1998.5-2002 Dodge Ram HD truck. It was notorious for early lift pump failures. The worst part is that the VP44 injection pump in these trucks was cooled and lubricated by fuel. If the lift pump fails, it can cause overheating and major damage.
If you own a Duramax, you might be thinking that since your truck doesn’t have a lift pump, you can’t benefit from an aftermarket one. However, installing an aftermarket lift pump system is a good way to prolong the life of the factory CP3 pumps on 2001-2010 models and back up the failure-prone CP4.2 pumps on the 2011-2016 GM trucks.
Upgrade or Replace with ProSource Diesel
When you need to upgrade or replace your lift pump or fuel pump system, ProSource Diesel offers a quality selection of aftermarket lift pumps and fuel pumps.
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The post Lift Pump vs Fuel Pump in Diesel Trucks appeared first on Prosource Diesel.
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