CP4 failure isn’t just a common issue—it’s a ticking time bomb sitting under the hood of thousands of diesel trucks. If you own a 2011–2016 Duramax, a 2011+ 6.7 Powerstroke, 2019-2020 6.7 Cummins, or a 2014–2023 Ram EcoDiesel, odds are you’ve got a CP4 pump running your fuel system. And if you haven’t heard about CP4 pump failure yet, you’re one bad tank of fuel away from learning the hard way.

So, what is a CP4 pump, and why does it take out the entire fuel system when it goes? In this post, we’ll break it down—how it works, why it fails, what it costs, and most importantly, how to protect your truck before it happens.

One failure can mean a $10,000 repair bill. But the right upgrades can make sure it doesn’t happen at all. Let’s get into it.

Understanding CP4 Failure: Symptoms, Causes & Upgrades

What Is a CP4 Pump and When Was it Used?

The CP4 pump is a high-pressure fuel injection pump designed by Bosch and rolled out in the early 2010s to meet stricter emissions standards. On paper, it was a step forward—smaller, lighter, and capable of delivering the fuel pressure needed for cleaner combustion. But in the real world? It’s earned a reputation for being one of the most failure-prone components in modern diesel trucks.

The CP4 was meant to replace the tried-and-true CP3, but it wasn’t built for today’s ultra-low sulfur diesel (ULSD). ULSD lacks the lubricity older fuels had, and the CP4’s internal roller-tappet design doesn’t hold up. Without enough lubrication, metal-on-metal contact starts grinding down the pump from the inside. The result? Shrapnel gets sent downstream and takes your whole fuel system with it.

And while the CP4 was supposed to be the next evolution, many diesel owners would argue it’s a step backward. We cover the full story in our blog on the return of the CP3 injection pump.

If your truck came with a CP4, this section will help you figure out if you’re at risk—and what generation of Duramax, Powerstroke, or EcoDiesel got stuck with the short end of the stick.

Duramax CP4

GM owners got hit first. The CP4 pump showed up in 2011 with the LML Duramax, running through the 2016 model year. While the engine itself was solid, the CP4 became the Achilles’ heel. Failures were common enough that GM ditched it completely with the launch of the L5P in 2017, which uses a Denso system instead.

If you’re running a 2011–2016 Duramax, you’ve got a CP4. And unless it’s already been swapped or upgraded, you’re sitting on borrowed time.

6.7 Powerstroke CP4 Pump

Ford followed suit in 2011, dropping the CP4 into the 6.7L Powerstroke. The pump is tucked deep in the engine valley, which makes service a pain—and replacement even worse. Lawsuits have hit Ford hard over this exact issue, with thousands of Powerstroke owners footing massive repair bills after a sudden CP4 failure.

Ram EcoDiesel CP4 Pump

Ram’s 3.0L EcoDiesel joined the CP4 club in 2014—and like its bigger Duramax and Powerstroke cousins, it didn’t take long for problems to surface. The CP4 pump was used in Ram 1500 EcoDiesel models from 2014 to 2023, and just like the others, it struggles with today’s low-lubricity ULSD fuel.

Failures in EcoDiesel trucks can be just as catastrophic, leading to full fuel system replacements and four-figure repair bills. And while these trucks are smaller in size, the cost of fixing a blown CP4 still hits just as hard.

What Causes CP4 Pump Failure?

The short answer? Bad design and bad fuel. The CP4 pump was never built to handle the lack of lubricity in today’s ultra-low sulfur diesel (ULSD). Bosch built it for cleaner emissions—not long-term durability—and that tradeoff shows up fast when you put real miles on a work truck.

Inside the CP4 is a roller-tappet cam setup that relies on fuel to lubricate the internals. But ULSD doesn’t provide enough slickness to keep those parts moving cleanly. Over time, metal-on-metal contact grinds down the cam lobes and rollers. Once that starts, it’s game over.

The worn-down metal turns into shavings, and those shavings get shot through the rest of the high-pressure fuel system—rails, injectors, lines, tank—contaminating everything. There’s no fail-safe. No internal screen. No early warning. Just a silent failure that takes out everything in its path.

And once it happens? You're not just replacing the pump—you’re replacing the entire system.

The scale of the problem hasn’t gone unnoticed—CP4 failures have become so widespread that they’ve sparked multiple class action lawsuits against GM and Ford.

CP4 Pump Failure Symptoms

The worst part about a CP4 pump failure is how little warning you get. One minute the truck’s running fine, the next you’re dealing with a crank-no-start and a $10,000 headache.

If you know what to watch for, you might catch it early—before it grenades your entire fuel system. Here’s what to look out for:

• Engine cranks but won’t start: If the pump grenades mid-drive or on startup, the fuel pressure will drop too low to fire the injectors.
• Reduced engine power: If the internal damage is just starting, you might feel sluggish acceleration or poor throttle response. That’s your pump starving the injectors.
• Metallic ticking or knocking: Once rollers or lobes start chewing themselves apart, you’ll hear it—usually a rhythmic ticking or light knock from the engine bay.
• Rough idle or sudden stall: As debris clogs up injectors or fuel delivery becomes inconsistent, you’ll notice misfires, stumble, or sudden shutdowns.
• Trouble codes: Look for DTCs like P0087, P0191, or P0088—all fuel rail pressure-related. They’re not always a smoking gun, but they’re worth paying attention to, especially if you’re seeing any of the above symptoms.

Bottom line: if you’re seeing any combo of these signs, shut it down. Keep running it, and you’re just grinding metal into every corner of your fuel system.

CP4 Pump Replacement: What Gets Damaged & What It Costs

When a CP4 pump lets go, it doesn’t just stop pumping fuel—it self-destructs from the inside out. The hardened steel internals grind against each other, sending microscopic metal shavings through every line, rail, and injector in the system. And once those shavings are in your fuel system, they don’t just disappear—they keep circulating, doing more damage with every key cycle.

Here’s what usually takes a hit after a CP4 failure:

• High-pressure fuel lines
• Fuel rails
• All injectors
• Low-pressure lift pump
• Fuel tank and pickup assembly
• Return lines and filters

In most cases, that means a full system teardown. You’re not just swapping in a new pump—you’re flushing the tank, replacing injectors, cleaning or replacing lines, and hoping the ECM didn’t freak out along the way.

Average repair cost? Anywhere from $8,000 to $12,000, depending on labor rates and parts availability. Some dealers will even try to upsell you on a new engine if the damage was severe enough.

All in all, there’s no “minor” CP4 failure. Once it starts to go, it takes everything down with it.

How to Prevent CP4 Failure

The best fix for a CP4 failure is making sure it never happens in the first place. While you can’t change the pump’s flawed design, there are proven ways to reduce the risk—and they’re a lot cheaper than replacing an entire fuel system.

CP4 Disaster Prevention Kit

This is the first line of defense. A CP4 disaster prevention kit reroutes fuel from the pump’s return line through an external filter. If the pump starts to break down and shed metal, the kit traps those particles before they reach your injectors, rails, or tank.

It won’t stop the pump from failing—but it can stop that failure from trashing everything else. For both Powerstroke and Duramax owners, it’s one of the smartest mods you can bolt on.

Diesel Fuel Additives

Next up: lubrication. As we’ve discussed, the CP4 relies on diesel fuel to keep its moving parts from chewing each other up. But modern ULSD doesn’t have the lubricating properties that older diesel used to, especially in colder temps or with long idle times.

That’s where fuel additives come in. Running a high-quality diesel additive helps restore lubricity, reduces wear inside the pump, and can even improve cold starts and fuel economy. Not all additives are created equal, though.

If you want a breakdown of what to look for—and why it matters—check out our full write-up on the benefits of using a diesel additive. It’ll walk you through how additives protect your CP4 and boost overall engine health.

CP4 Pump Upgrade Options

If you’re sticking with a CP4, upgrading to a stronger version is better than rolling the dice on stock. Some Bosch and aftermarket CP4 pumps have been updated with more durable internal components—think hardened cam lobes, stronger rollers, and tighter machining tolerances.

These upgrades can reduce the risk of failure, especially when paired with a disaster prevention kit and fuel additive. But let’s be clear: it’s still a CP4. The core design hasn’t changed, and it’s still running on fuel that doesn’t give it the lubrication it really needs.

That said, for owners who want to avoid the cost of a full conversion, an upgraded CP4 pump can buy you time and peace of mind—just don’t confuse it for a permanent solution.

CP4 Conversion Options

If you’re done gambling on the CP4 and ready to upgrade to something more reliable, there are two main routes: CP3 or DCR. Both eliminate the CP4’s weak points, but they do it in different ways.

CP4 Pump vs CP3

The CP4 was built specifically to run at sustained higher pressure compared to a CP3. The CP3 was built for durability.

• CP4: Higher pressure, lighter weight, but fragile internals and poor tolerance for ULSD
• CP3: Proven design, better fuel lubrication handling, fewer moving parts to fail

CP4 to CP3 Conversion

A CP4 to CP3 conversion replaces your CP4 with a retrofitted CP3 system. These kits are The CP4 to CP3 conversion is one of the most proven ways to eliminate CP4-related failures—especially for 2011–2016 LML Duramax trucks. This generation is notorious for pump issues, and GM made the swap relatively painless. Most kits include everything you need: pump, lines, hardware, and in many cases, no tuning is required.

The CP3 has a legendary track record for durability. Swapping it in means fewer moving parts, better tolerance for ULSD, and real peace of mind. If you're ready to ditch the CP4 for good, check out our CP4 to CP3 conversion kit from Industrial Injection—it’s a direct-fit solution for 2011–2016 LML Duramax trucks.

For Powerstroke owners, most Super Duty owners go the DCR route instead of the CP3 for unsurpassed reliability.

CP4 to DCR conversion

For 6.7 Powerstroke owners, a DCR (Digital Controlled Rail) pump is the best alternative to a CP4. Unlike the CP3 swap into a Powerstroke —which requires tuning and often emissions work—the DCR is a true drop-in replacement that keeps everything emissions-compliant and plug-and-play.

The DCR pump ditches the roller-tappet design that made the CP4 so fragile. Instead, it runs a brushless motor and is electronically controlled for cleaner, more efficient fuel delivery. No tuning, no complicated retrofitting—just a smarter, stronger pump that fits like stock.

If you're looking for a bolt-on solution that doesn’t compromise reliability or compliance, check out this CP4 to DCR pump conversion kit for 2011–2024 Ford 6.7L Powerstroke trucks.

CP4 Pump Frequently Asked Questions

What trucks have CP4 pump?

Trucks equipped with a CP4 pump include:

• 2011–2016 GM 6.6L Duramax (LML)
• 2011–2025 Ford 6.7L Powerstroke
• 2014–2023 Ram 3.0L EcoDiesel
• 2019-2020 Ram 6.7L Cummins

If your truck falls within these years, you’re likely running a CP4—and at risk of failure if it hasn’t been replaced or protected.

What year Duramax has the CP4 pump?

The 2011 to 2016 LML Duramax models came with the CP4 pump from the factory. Starting in 2017, GM switched to the L5P platform with a different injection system that doesn’t use the CP4.

Where is the CP4 pump located 6.7 Powerstroke?

The CP4 pump is located in the engine valley of the 6.7 Powerstroke—between the cylinder heads, toward the front-center of the engine. It’s not easy to reach, which makes replacement more labor-intensive than on some other platforms.

How long does a CP4 pump last?

A CP4 pump typically lasts anywhere from 50,000 to 150,000+ miles, depending on fuel quality, additive use, driving conditions, and luck. There’s no set lifespan, and many fail without warning.

What does CP4 pump replacement cost?

Replacing a failed CP4 usually means replacing the entire fuel system. Expect to pay $7,500 to $12,000 or more, depending on how much contamination occurred and whether you’re using OEM or upgraded components.

Protect Your Truck from CP4 Failure with Diesel Power Products

Whether you’re driving a hard-working Powerstroke or an LML Duramax, the CP4 pump is a weak link you can’t afford to ignore. It wasn’t built for today’s fuel—and it shows.

But now you know what to watch for, what fails, and what your upgrade options are. From prevention kits and lubricity additives to full conversion systems, there’s more than one way to get ahead of a CP4 failure—and we’ve got every one of them.

• Want peace of mind?
• Want to keep your truck on the road where it belongs?
• Want gear that’s been proven in real-world conditions?

Start with the parts diesel owners trust—CP4 disaster prevention kits, fuel additives, and conversion options built to outlast.

Whatever route you take, Diesel Power Products has your back.