Let's not sugarcoat it: there's a relatively cheap part bolted to your late-model diesel that's quietly waiting to detonate a $12,000 repair. It's the Bosch CP4.2 high-pressure fuel pump, and when it grenades, it doesn't ask permission — it machine-guns metal shrapnel through your entire fuel system and leaves you stranded with a five-figure bill. Don't be that guy.

The fix is cheap, it's proven, and it's the single smartest insurance policy you can bolt to a 6.7 Power Stroke, Duramax, or 6.7 Cummins. Here's exactly how the CP4 kills trucks — and how S&S Diesel Motorsport shuts the problem down for good. Want it handled by people who've done a hundred of them? Send us your build and we'll spec it.

What is the CP4 pump (and is it bolted to your truck)?

The CP4.2 is the high-pressure injection pump that squeezes diesel up to 30,000+ PSI so your common-rail injectors can atomize it. Bosch built it lighter and more efficient than the bulletproof CP3 it replaced — and "lighter and more efficient" is engineer-speak for "less margin for error." Manufacturers slapped it on nearly every light-duty diesel of the last decade to chase emissions and fuel-economy numbers.

If you're running any of these, you've got a CP4 ticking away:

• Ford 6.7L Power Stroke — 2011 and up
• GM Duramax — 2011–2016 LML and 2017+ L5P
• RAM 6.7L Cummins — 2019 and up (5th gen)

So whether you're shopping Power Stroke, Duramax, or late-model Cummins parts, this is your problem too. And no — there's no magic tune or additive that makes the design bulletproof. The only real answers are mechanical.

Where is the CP4 located?

On the 6.7 Power Stroke it lives in the engine valley under the intake — which is exactly why a failure is such a nightmare to clean up. On the Duramax and Cummins it's engine-mounted and driven off the front of the engine. Wherever it sits, the failure mode is the same: it sends debris downstream, and downstream is everything expensive.

Why the CP4 grenades — the short, brutal version

The CP4 runs two pistons off a cam and a roller "follower." That follower is supposed to ride the cam smoothly, lubricated by the diesel fuel itself. Here's the catch: U.S. ultra-low-sulfur diesel (ULSD) has garbage lubricity compared to the European fuel Bosch validated the pump on. Add one dry start, one bad tank, or just normal wear, and that follower can rotate out of position.

Once it does, it's metal-on-metal at extreme pressure. The pump starts shaving itself into microscopic (and not-so-microscopic) chips and pumps that glitter everywhere — high-pressure lines, fuel rail, every injector, the tank. That's why a CP4 failure is never "just a pump." You're staring down injectors, rails, lines, sensors, a full flush, and labor. Real-world bills routinely land between $8,000 and $12,000+. On some trucks it's totaled an entire fuel system in a single highway pull.

The CP4 problem, platform by platform

The failure mode is universal, but the details (and the drama) differ by truck.

Ford 6.7L Power Stroke (2011+)

Ford ran the CP4 on the 6.7 Power Stroke from its 2011 debut. Because the pump is buried in the valley, a failure is brutal — contaminated fuel reaches the injectors fast, and cleanup means pulling a huge chunk of the top end. The 2011–2016 trucks are the ones you'll see grenade most often simply because they've racked up the miles. If you've got a high-mileage 6.7 PSD and no protection, you're running on borrowed time.

GM Duramax LML & L5P (2011+)

GM switched to the CP4 on the 2011–2016 LML and carried it into the 2017+ L5P. The earlier LBZ and LMM trucks used the tougher CP3, which is why so many Duramax guys swear by a CP3 swap. The LML failures got bad enough to spark a class-action lawsuit — the "cp4 fuel pump Silverado/Sierra lawsuit" you've seen searched is very real.

RAM 6.7L Cummins (2019+)

The 5th-gen 2019+ Cummins is the newcomer to the CP4 club. Because these trucks are newer, the failure wave is still building — but the same design flaw is baked in. The smart Cummins owners are getting ahead of it now, while protection is cheap and the truck is healthy. Building one anyway? See the first 5 upgrades for a 6.7 Cummins.

"Didn't they recall this?" — the lawsuit reality

This is the part that makes owners furious. The CP4 disaster is so widespread it's spawned class-action lawsuits against Ford and GM — search "cp4 fuel pump Silverado/Sierra lawsuit" or "Ford CP4 recall" and you'll fall down a rabbit hole of angry owners. But here's the cold truth: there is no blanket recall that redesigns the pump. Litigation drags on for years; your truck still has the same time bomb. Waiting for a manufacturer to save you is how you end up paying $12k out of pocket. Protecting it is 100% on you.

Symptoms of a dying CP4 (don't ignore these)

Sometimes the CP4 goes from fine to fragged with zero warning. But when it does telegraph trouble, it looks like:

• Hard starting, long cranking, or a flat no-start
• Sudden power loss, stumbling, or limp mode
• Rough running or misfires under load
• Metal glitter in the fuel filter — if you ever see this, stop driving
• Rail-pressure or fuel-system fault codes

How to check your fuel for contamination

Next time you service your fuel filters, cut the old one open and look closely at the media under good light. Clean diesel residue is one thing; metallic sparkle is a five-alarm fire. If you see glitter, do not keep driving — every mile pushes more debris into your injectors. By the time you've got hard symptoms, contamination is usually already loose in the system. That's the whole argument here: the cheapest CP4 failure is the one that never reaches your injectors.

Fix #1: The S&S CP4 Disaster Prevention Kit (cheap insurance)

A CP4 Disaster Prevention Kit (a.k.a. bypass kit) is the most cost-effective move you can make. It re-routes the pump's return circuit so that if the CP4 starts eating itself, the debris gets captured and bypassed instead of being shoved forward into your injectors and rails.

Translation: it doesn't stop the pump from wearing out someday — it stops a dying pump from taking the entire fuel system to the grave with it. When a protected pump finally lets go, you replace a pump. Not a pump and eight injectors and rails and lines and a weekend of labor.

The S&S Diesel prevention kits are application-specific — dedicated versions for 6.7 Power Stroke, Duramax, and 6.7 Cummins — so fitment matters. Grab the right one from our diesel fuel system lineup, and if you're not 100% sure which version your year and platform needs, send us your truck details and we'll confirm it before you spend a dime.

Who needs a prevention kit? Basically everyone.

If you've got a CP4 and a pulse, run one. It's cheap relative to the catastrophe it prevents, it bolts on for any competent installer, and it doesn't change how the truck drives. It's the ultimate set-it-and-forget-it reliability mod.

Fix #2: The S&S DCR conversion (kill the problem entirely)

Want to eliminate the CP4 risk instead of just containing it? Then get rid of the CP4. That's what the S&S DCR (Disaster-resistant) pump conversion does — it yanks the fragile CP4 and replaces it with a far stouter pump built in the spirit of the legendary CP3, engineered to survive the lubrication conditions that murder the CP4.

Why builders love the DCR route:

• It deletes the failure mode — not mitigates it, deletes it
• More fueling headroom for tuned trucks chasing big power
• Total peace of mind on high-mile rigs and trucks you actually depend on

It's a bigger up-front spend than a prevention kit, but for built trucks, tow rigs, and forever-trucks it's the gold standard. We dig into the full debate in our companion guide on CP4 vs CP3 conversions — read that if you're weighing the swap. The S&S lineup covers conversions for the major platforms, and we can bundle it with fresh injectors while the system's open.

Prevention Kit vs. DCR Conversion — pick your weapon

Rule of thumb: stock truck and you just want cheap insurance? Start with a prevention kit. Tuning, towing heavy, or planning to keep the truck past 200k? The DCR conversion pays for itself the first time it saves your injectors.

Will a lift pump or fuel additive save my CP4?

Short answer: they help the odds, but they don't fix the design. Here's the honest breakdown:

• Lift pumps & filtration — A quality lift pump delivers clean, air-free, consistent fuel to the CP4, which absolutely reduces stress and buys you margin. It's smart insurance and great for power. But it can't undo the CP4's fundamental lubrication weakness. Pair it with — not instead of — a disaster prevention kit. Dig into options in our best diesel lift pumps guide.
• Lubricity additives — A good additive raises ULSD's lubricity back toward what the pump wants, and running one every tank is cheap insurance. But additives are a band-aid, not a cure — miss a few tanks, grab one bad fill-up, and you're exposed again.

Bottom line: additives and lift pumps are the seatbelt. The disaster prevention kit or DCR conversion is the airbag. Run them together.

What a CP4 failure actually costs vs. protecting it

Let's do the math that matters. Here's roughly what a full grenade puts on the table:

There is no scenario where "I'll risk it" comes out ahead. Spend a little now, or a fortune later. That's the whole pitch, and it's the truth.

The supporting cast: clean fuel keeps the CP4 alive longer

The CP4 lives and dies on the quality and consistency of the fuel feeding it. Aerated, dirty, or pressure-starved fuel is exactly what accelerates the failure — which is why smart owners pair CP4 protection with a serious lift pump and filtration setup. Round out the package from our fuel system collection, and if you're stacking injectors at the same time, browse our injector selection while the system's apart.

What S&S Diesel Motorsport actually builds

S&S didn't earn its reputation by accident — they live and breathe diesel fuel systems, and their engineering is genuinely best-in-class. That's why we stock them. When you shop the S&S Diesel collection at DNR Customs, you'll find the parts that attack the CP4 problem from every angle, plus the fueling hardware to back a serious build:

• CP4 Disaster Prevention Kits — application-specific bypass kits for the 6.7 Power Stroke, Duramax, and 6.7 Cummins. The cheapest insurance in diesel.
• DCR pump conversions — full CP4-delete kits that yank the weak pump and drop in a stout, disaster-resistant unit. Set-and-forget peace of mind.
• CP3 conversions — the classic bulletproof swap for owners who want the old-school workhorse pump back. We compare the routes head-to-head in our CP4 vs CP3 conversion guide.
• Performance injectors & pumps — when you're chasing big power and need fueling capacity to match the airflow. Browse injectors and the wider fuel system selection.

The hardest part for most owners isn't installing the parts — it's knowing which parts their specific year, engine, and power goals actually call for. Order the wrong version and you're shipping it back; stack the wrong combo and you leave power (or reliability) on the table. That's exactly the headache our team kills for you. Tell us what you're working with and what you want out of the truck, and we'll build a parts list that makes sense the first time.

Best practices once you're protected

Bolting on protection is step one. Keeping the whole fuel system healthy is step two — and it's the difference between a truck that runs hard for years and one that surprises you with a tow bill anyway. A few habits that keep any CP4-equipped diesel happy:

• Run a lubricity additive every tank. It's pennies per fill-up and directly addresses the low-lubricity ULSD that stresses the pump in the first place.
• Service your fuel filters on schedule — and cut the old ones open to inspect the media for any metallic sparkle. Early detection saves injectors.
• Never run the tank down to fumes. Low fuel means more heat and aeration reaching the pump, and heat is the enemy.
• Add a quality lift pump for clean, consistent, air-free supply pressure — the single best supporting upgrade. Start with our diesel lift pump guide.
• Act fast on warning signs. Rough running, hard starts, or glitter in a filter means stop and inspect now, not next weekend.

Do that, and a protected CP4 truck will reward you with years of trouble-free miles. Ignore it, and the CP4 will eventually remind you why this article exists.

Frequently asked questions

What is a CP4 pump?

The Bosch CP4.2 high-pressure fuel pump found on most 2011+ light-duty diesels. It builds the extreme pressure common-rail injection needs — and it's infamous for a failure mode that contaminates the entire fuel system.

What trucks have the CP4 pump?

2011+ Ford 6.7L Power Stroke, 2011–2016 LML and 2017+ L5P GM Duramax, and 2019+ RAM 6.7L Cummins. Not sure about yours? Ask us and we'll confirm in minutes.

What year Duramax has the CP4 pump?

The 2011–2016 LML and the 2017+ L5P both run a CP4. The earlier LBZ/LMM trucks used the tougher CP3.

Did Ford recall the CP4 pump?

No blanket recall that redesigns the pump exists. The issue has played out through class-action litigation — which doesn't help your truck today. Aftermarket protection does.

How long does a CP4 pump last?

There's no set number — some go 200k+ miles, others let go early. That unpredictability is exactly why prevention beats waiting for symptoms.

Will a lift pump prevent CP4 failure?

It reduces the risk by feeding the pump clean, consistent fuel, but it can't eliminate the design flaw. Use a lift pump and a disaster prevention kit (or a DCR conversion).

How much does a CP4 failure cost?

Because it contaminates injectors, rails, and lines, full repairs commonly run $8,000–$12,000+. A prevention kit costs a tiny fraction of that.

Can I install a disaster prevention kit myself?

Experienced DIYers can, but fuel work is unforgiving and fitment is year/platform-specific. Want it done right — or bundled with injectors or a DCR conversion? Our certified diesel techs will handle it. Just request a quote.

Protect it before the CP4 picks the timing

For most of these trucks a CP4 failure isn't if — it's when. The smart money armors the fuel system before the grenade goes off, not after the tow truck shows up. Whether that's an affordable disaster prevention kit or a bulletproof DCR conversion, S&S Diesel builds the parts that get it done.

Shop the full S&S Diesel Motorsport collection at DNR Customs, browse related fuel system upgrades, and if you want a human to spec the exact kit for your year and platform, request a quote — we'll make sure you order the right part the first time, every time.