2001-2006 5.9 Cummins Lift Pump Location (Problems Guide)
One thing about spotting the location of different components is: Those locations will change depending on the era the motor was made. In the Cummins case, it changed to a 24-valve system and computer, not mechanical, operations about this time.
When it comes to the 2003 Holiday Rambler Neptune model, the lift pump is located on the engine just above the starter motor. This location would be on the passenger side of the coach. We cannot vouch for the location on other models at this time.
To learn more about this location just continue to read our article. It explores the issue so you have the best information possible to find your individual lifter pump. Take a few minutes to see how this information helps you.
Cummins Lift Pump 101
Does a 5.9 Cummins Have a Lift Pump?
The good news, if you can call it that, is that there is a lift pump on the later models of the 5.9 Cummins engine. This part was installed when Cummins went to the 24-valve system and it was part of a three-component fuel injection system.
There was the lift pump, the injector pump, and the injectors in this system. The purpose of the lift pump was to move the fuel from the fuel tank to the injector pump. The latter pump could not do this work alone.
If it did, the injector pump would fail and you would have a nice repair bill waiting for you after it was fixed. To protect the injector pump from working far too hard, Cummins installed the lift pump to help get the fuel to the engine.
It is a vital part of the motor as you will soon see.
What Does a Lift Pump do For a 5.9 Cummins?
As we just mentioned, the main duty of the lift pump was to protect the injector pump from being over-stressed and working too hard. It is a long way from the fuel tank to the engine and for the injector pump to handle all the work was asking too much.
Cummins installed the lift pump to alleviate the distance problem. The lift pump’s other duty was to pull the fuel out of the fuel tank and send it to the injector pump.
So instead of the injector pump working too hard, the stress was placed on the lift pump. This only changed the problem of a pump failure from one pump to the other one in this system.
This system was in place between 1998 and 2004 but what Cummins did for the last 3 production years is something for another article. The 5.9 Cummins engine was replaced by the 6.7 Cummins in 2007 or 2008.
5.9 Cummins Lift Pump Location
Up until 1998, the 5.9 Cummins was a 12-valve engine. This may cause some design differences between it and the 24-valve 5.9 that replaced this model. The lift pump location for this particular model is not in a very easy to reach position.
From what we can see, the lift pump is located between the firewall and the engine block, down below the master cylinder, and just off to the left if you are facing the truck.
You will have to disconnect or loosen several parts to be able to reach the lift pump and remove it safely. If you want to see the location and see what you need to do to remove this pump, check the video below.
24v Cummins Lift Pump Location
There seems to have been a design change when Cummins went to a 24-valve 5.9 engine in 1998. They made the change about halfway through the year so you will see the year marked as 1998.5 and it goes to about 2002 for this particular location.
The lift pump for this specific model is behind the fuel filter and a few other components. You do have to disconnect different wires and cables to get to it. The fuel filter is on the driver’s side of the engine and the lift pump is behind that.
In many cases, the lift pump was attached directly to the engine. Below there's another YouTube video that shows you where the lift pump will be on the 1998.5 to 2002 5.9 Cummins motor.
This location caused a lot of problems for the lift pump. One of those problems was the excess heat it had to face while the engine was running. That was because the lift pump was attached directly to the block.
The other problem that caused this lift pump to fail often was that it had to pull the fuel a very long way. This added stress caused premature pump failure. It also caused Cummins to redesign the location for the 2005 to 2007 5.9 models.
That new location was inside the fuel tank and this made the lift pump more reliable. It may not have failed as often once this move was made.
How do I Know If My Lift Pump is Weak?
Like all components, there will be symptoms or signs that you have a problem with the lift pump. Here are some of those symptoms or signs that will tell you that there is a problem:
- Engine misfires
- Lean AFRs
- Rough idling and poor performance
- Hard starting or engine stalling while running
- Boost below target
Upon seeing these signs many 5.9 Cummins owners went to an aftermarket lift pump. They were able to put them in a new location that spared them from the heat and shortened the distance to pull the fuel from the tank.
The location of these aftermarket pumps was not in the fuel tank itself but a little closer to it. The drawback to making this switch was the cost. Aftermarket lift pumps for a Cummins engine can get expensive.
The expense was offset by the new reliability of the pump. That may be a good trade-off for many people.
5.9 Cummins Lift Pump Failure Symptoms
Besides the problems mentioned in the previous section, one thing you should know is that the lift pump can fail without any warning. In other words, you won’t see any symptoms.
Then to make matters worse, the failed lift pump usually does not throw any codes. Not to mention that the injector pump can still draw fuel from the fuel tank if the lift pump goes out.
The only way to be sure if the lift pump is really bad, and this is for a 2004 model, is by using a fuel pressure gauge. If you turn the key on, you may hear the lift pump run for about 3 seconds. But it can run and still not move any fuel.
To see if the lift pump is not moving any fuel, open the drain line and see if any fuel is coming out. Make sure to have a container to catch any fuel that does exit the lift pump.
5.9 Cummins Lift Pump Problems
We have addressed this earlier. The two main problems with this pump were the original location. The close to or directly attached locations for the lift pump caused it to be exposed to an excessive amount of heat.
This heat did place about as much stress on the pump as the distance to the fuel tank did. That was the second major problem with the lift pump.
It had too far to pump the fuel for it to have a long lifespan. That extra work also added a lot of stress so the pump would fail prematurely. The two issues were enough for Cummins to finally change the location of the pump to the fuel tank.
5.9 Cummins Lift Pump Bypass
There are some kits available to help you do the bypass of the OEM lift pump. There is still a pump involved with the kit but it is located closer to the fuel tank and further from the heat of the engine.
This may make it more accessible as well as make the pump more reliable. One kit is designed to bypass the lift pump located behind the fuel filter. However, it is not a cheap replacement and can cost over $400.
A good internet search will provide numerous options to bypass your original lift pump. Just make sure to compare prices before you buy.
Some Additional Words
When it comes to engine components, not every engine maker gets it right the first time. This seems to be the case with the lift pump and Cummins's initial designs.
While placing it behind the fuel filter may have been a good idea, placing it directly on the block was not. Nor was it a good idea to place it a great distance away from the fuel tank.
The original location of the lift pump was a disaster waiting to happen. It happened often.
