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If you own a 2003-2007 Dodge Ram with the 5.9L Cummins, a leaking high-pressure injector line is a problem worth addressing quickly.
The injector lines on these common rail Cummins engines are known to crack, and the #4 injector line is a particularly common trouble spot. In many cases, the issue starts with the injector line clamp. When the original clamp loosens or fails, the high-pressure line can vibrate more than it should. Over time, that movement can contribute to cracking and a high-pressure fuel leak.
The good news is that there is an updated replacement available, and years of customer feedback tell a pretty consistent story: it fits correctly, addresses the problem, and gets trucks back on the road.
A cracked injector line can create some obvious symptoms.
You may notice:
A strong diesel fuel smell
Fuel inside the engine compartment
Visible fuel spraying or leaking around an injector line
Difficulty maintaining rail pressure
Poor running or a truck that will no longer stay running
Because these are high-pressure fuel lines, even a relatively small failure can create a serious mess.
On the truck featured in our Thoroughbred Diesel repair video, the #4 injector line clamp had completely failed. The line could move inside the rubber isolator, allowing excessive vibration. A crack eventually developed near the injector-side portion of the line.
For the #4 cylinder, the replacement shown in our installation video is the Cummins Injector Fuel Supply Tube #4, part number 5289447.
Shop the Cummins 5289447 #4 Injector Fuel Supply Tube
The updated line uses a different clamp design than the older line removed from the truck.
Instead of the original sandwich-style clamp with a bolt that can loosen, the updated line uses a rolled steel clamp design. This provides a more secure way to support the injector line and reduces the opportunity for the clamp itself to loosen and allow excessive movement.
That's one of the reasons this isn't simply a replacement for a cracked line. It's an updated solution to the issue demonstrated on the original part.
We can explain the design all day, but customer feedback provides another useful perspective.
Owners who have purchased the Cummins 5289447 injector line repeatedly mention the same things: correct fitment, improved design, straightforward installation, and successful repairs.
Fitment is probably the most common theme in the customer reviews.
Owners have described the line as:
"Perfect fit!"
"Fit great, works great."
"Exactly what I needed, fits perfectly."
"The part fit perfectly."
"Fit like it should."
That's important with a high-pressure fuel line. You're not looking for something that almost fits or needs to be bent into position. You want the correct line for the application.
Several customers specifically commented on the updated design rather than simply saying the part worked.
One customer called it a "great fix for the faulty design of the OEM line."
Another said the replacement "resolved the original design flaw at the same time."
Other comments included:
"Better design"
"Better style than the stock type"
"Think this new design will be much better"
"10/10 would buy again if need be, but shouldn't have to for a while with the upgraded style injector line."
That lines up closely with what Wade demonstrates in our installation video. The original line had a failed clamp that allowed excessive movement, while the updated replacement uses the revised rolled steel clamp.
The most useful reviews aren't always the ones that simply say "great product."
They're the ones that tell us what happened after the repair.
One customer installed the line after following our YouTube installation video, test drove the truck, and reported that everything appeared fixed and back to normal.
Another customer summed it up even more simply:
"Worked Great! Thanks"
When you're dealing with a fuel leak on a truck you depend on, that's really the result that matters.
One of our favorite reviews came from a customer who needed his truck for an upcoming family RV trip.
He had reserved an RV and a campsite and needed his Dodge Cummins running in order to make the trip happen.
After identifying the injector line problem, he watched our repair video, ordered the replacement fuel line, requested expedited shipping, and called Thoroughbred Diesel to make sure everything was on track.
The line arrived, he completed the repair, and the family made the trip without any further issues.
That's a pretty good example of why we make installation videos in the first place.
Sometimes you don't just need a part. You need to understand what's wrong, know you're ordering the right part, and have enough information to confidently make the repair.
If your #4 injector line has failed and the other lines are in good condition, you can replace the individual line.
Shop the Cummins 5289447 #4 Injector Line
However, some owners would rather replace all six high-pressure injector lines at the same time, particularly if they're working on an older truck and want to update the entire set.
Thoroughbred Diesel offers several complete injector line options for the 2003-2007 5.9L Cummins.
If you want to stay with Cummins replacement parts, we offer a complete set of injector supply lines.
Shop the Cummins 2003-2007 5.9L Injector Supply Line Set
This is a good option for owners who would rather replace the complete set instead of addressing the lines individually as they age.
We also offer complete fuel injection line options from Fleece Performance.
Shop Fleece Performance Fuel Injection Lines
BD Diesel is another option for 5.9L Cummins owners looking to replace or upgrade their injector lines.
Shop BD Diesel Injector Lines
The right choice depends on your truck, your goals, and whether you're repairing one failed line or replacing the complete set.
The repair is fairly straightforward if you're comfortable working on the common rail fuel system, but there are a few details you don't want to overlook.
In our installation video, Wade walks through the complete replacement process, including how to hold the injector feed tube retaining nut while loosening the line so the feed tube doesn't turn inside the cylinder head.
Some of the key tools used include:
19mm wrench
24mm open-end wrench
24mm socket
10mm socket
19mm crow's foot
Torque wrench
The feed tube retaining nut is checked at 37 ft-lbs, and the high-pressure injector line connections are torqued to 22 ft-lbs in the installation demonstrated in the video.
If you're planning to tackle the repair yourself, we'd recommend watching the full installation before getting started.
A cracked injector line on a 2003-2007 5.9L Cummins isn't something we'd recommend putting off.
If you're smelling diesel fuel, finding fuel around the engine, or dealing with rail-pressure problems, inspect the high-pressure injector lines and their clamps.
If the #4 line is the problem, the Cummins 5289447 Injector Fuel Supply Tube gives you the updated replacement discussed in our installation video and backed by years of positive customer feedback.
And if you want to replace the complete set, you have several options:
Cummins Complete Injector Line Set
Fleece Performance Fuel Injection Lines
BD Diesel Injector Lines
Not sure whether you need one line or the complete set?
Call for Free Advice.
The Thoroughbred Diesel team can help you identify the problem and choose the right injector line solution for your 5.9L Cummins.