Quick Comparison
| Product | Best For | Est. Price | Rating |
|---|---|---|---|
| S&S Diesel Motorsport CP3 Conversion | Best Overall | ~$1800-2400 | 4.7/5 |
| Sinister Diesel CP4 Bypass | Best Budget | ~$180-250 | 4.6/5 |
| Exergy Performance CP4 Disaster Kit | Best Premium | ~$260-340 | 4.7/5 |
| Industrial Injection CP4 Bypass Kit | Best for L5P | ~$230-300 | 4.5/5 |
| FASS Fuel Systems CP4.2 Bypass | Best Compact | ~$200-280 | 4.6/5 |
Intro
If you own a diesel truck with a Bosch CP4 fuel pump. particularly a 6.7L Power Stroke or LML/LGH Duramax. you have likely heard the horror stories. When the CP4 fails, it does not go quietly. Metal debris from the disintegrating pump travels downstream through the entire fuel system, destroying injectors, rails, and lines. The repair bill routinely lands between $8,000 and $20,000. For many owners, it is a catastrophic and unplanned expense.
The good news is that CP4 failures are largely preventable. A properly chosen disaster prevention kit. sometimes called a CP4 failure prevention kit or fuel lubricity kit. addresses the root cause: insufficient lubrication from American ultra-low sulfur diesel fuel. In 2026, the aftermarket has matured significantly and there are several well-engineered options available. This guide covers the five best.
Top 5 Picks
1. FASS Titanium Fuel Air Separation System The most comprehensive CP4 protection solution available. The FASS system installs as a lift pump that draws fuel before it reaches the CP4, filtering and separating air and water while increasing fuel pressure and lubricity delivery to the pump. It effectively de-stresses the CP4’s internal tolerances and is widely regarded as the most thorough single-unit prevention approach.
2. AirDog II-4G Fuel Air Separation System A strong competitor to the FASS system and preferred by many fleet operators for its reliability record. The AirDog II-4G provides pre-pump filtration, fuel pressurization, and air/water separation in a compact unit. Installation is moderately involved but well-documented, and customer support from the manufacturer is consistently rated highly.
3. Exergy Performance CP4 Disaster Prevention Kit A more targeted and affordable kit specifically marketed as CP4 failure prevention. The Exergy kit introduces a lubricity additive dosing system into the fuel return line, ensuring the pump receives adequately lubricated fuel regardless of the ULSD fuel quality at your pump. Easier to install than a full lift pump system and a popular first-step solution for many owners.
4. S&S Diesel Motorsport CP4 Disaster Prevention Kit S&S Diesel is one of the most respected names in diesel fuel system work, and their CP4 kit reflects that expertise. It combines a fuel lubricity additive injection system with a bypass filtration approach that catches early metal contamination before it reaches downstream components. A strong middle-ground option between a full lift pump install and a simple additive kit.
5. PureFlow AirDog Raptor RP-150 Lift Pump Kit A more budget-accessible lift pump option that still provides meaningful CP4 protection via pre-pump filtration and pressure regulation. Not quite as feature-rich as the full FASS or AirDog II-4G systems, but a solid step up from additive-only solutions. A good option for owners who want hardware-based protection without the cost of a top-tier system.
What to Look For
Protection approach is the primary decision. Lift pump systems (FASS, AirDog, Raptor) are the most comprehensive. they address fuel quality before it reaches the CP4 with filtration, air separation, and pressurization. Additive-dosing kits (Exergy, S&S) are simpler to install but rely on chemical intervention. For trucks used heavily or for towing, lift pump systems offer superior long-term protection.
Installation complexity varies significantly. Lift pump systems require tapping into fuel lines and mounting a secondary unit, which takes several hours and basic mechanical knowledge. Additive kits are simpler and can often be installed in under an hour. Know your mechanical ability before choosing.
Compatibility is critical. Not all kits fit all affected trucks. Confirm fitment specifically for your year, make, and engine code before purchasing. LML and LGH Duramax installs differ from each other, and Power Stroke installs have their own specific configurations.
Filtration rating matters if you also care about fuel system cleanliness. Look for systems that filter to at least 2 microns. better systems go to 1 micron, which is more effective at catching early CP4 debris if failure begins.
Final Thoughts
If your truck has a CP4 pump and you plan to keep it, prevention is not optional. it is a financial decision. The FASS Titanium system is the top recommendation for owners who want the most comprehensive protection and are comfortable with the installation. For a simpler, more accessible approach, the Exergy or S&S Diesel kits provide meaningful protection at a lower cost and easier install.
Do not wait for the warning signs. By the time the CP4 is failing, the contamination is already spreading. The cost of a prevention kit is a fraction of what a full fuel system replacement will run. and the peace of mind is worth every dollar.
Frequently asked questions
What is a CP4 pump and why does it fail?+
The CP4 (Bosch CP4.1) is a high-pressure fuel injection pump used in 6.7L Power Stroke and LML/LGH Duramax diesel engines. It fails due to inadequate lubricity from American ultra-low sulfur diesel (ULSD) fuel, which has lower lubricity than European diesel. When the CP4 fails, metal shavings contaminate the entire fuel system, leading to injector and rail damage that can cost $8,000-$20,000 to repair.
Do CP4 disaster prevention kits void the factory warranty?+
Most CP4 disaster prevention kits are designed to be non-invasive and should not void the factory powertrain warranty under the Magnuson-Moss Warranty Act, but this is not guaranteed. Some kits tap into the fuel return line, which may be flagged at a dealership inspection. If your truck is still under factory warranty, consult with your dealer or a warranty specialist before installing any fuel system modification kit.
What vehicles are at risk for CP4 pump failure?+
Vehicles most commonly at risk include 2011-2016 Ford 6.7L Power Stroke diesels and 2011-2016 GM/Chevy LML and LGH Duramax engines. Some 2017+ 6.7L Power Stroke trucks also use a CP4-style pump. Ram 6.7L Cummins trucks are not affected as they use a different CP3 pump design that handles ULSD lubricity much better and does not share the same failure mode.