The Bosch CP4.2 High-Pressure Fuel Pump --- One of the Most Common Ford 6.7L Power Stroke Engine Problems

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Codenamed the Scorpion during its developmental stage, the 6.7L Power Stroke is Ford's in-house built diesel engine for the Ford Super Duty. Ford chose to design, engineer, and produce its own diesel engine to maintain profitability and a competitive edge in the growing diesel segment. This is the first Power Stroke not manufactured by long time partner, International Navistar. The absence of a partner seems to have given Ford an advantage over competitors, granting them the freedom to design an engine that fits their specific needs and the needs of their customers.

Ford 6.7L Power Stroke Engine

The Success of Ford 6.7L Power Stroke Engine

Fortunately, Ford seems to have hit a home run with the 6.7L, which impresses in the departments of performance, fuel economy, reliability, and as we're slowly finding out, longevity. Over 500,000 6.7L Power Strokes were sold in the engine's first three years of production.

The "six-seven" has proven itself to be a good engine in the near-decade it has been around. There are three generations of the powerplant: 2011-2014 (First), 2015-2019 (Second), and the Third-gen torque monster (1,050 lb-ft) found in 2020-2021 F-Series trucks.

The Bosch CP4.2 Failure

Through the years, we've found that first-gen Ford 6.7L diesels are the most problematic, and today we'll talk about the CP4.2 high-pressure fuel pump.

The Bosch CP4.2 high-pressure fuel pump at the heart of the common-rail system has a design flaw—and it's a shortcoming that can cause the pump to self-destruct. The Bosch CP4.2, is known for breaking down due to metal-on-metal contact that is promoted by air inside the pump. The contamination can completely destroy the fuel system (injectors, pressure regulators, lines, etc.) and take the fuel rails and injectors out with it. People have no choice but replace the CP4.2 pump altogether, which are very expensive repairs.

The Bosch CP4.2 High-Pressure Fuel Pump Ford 6.7L Power Stroke Engine

What You Can Do to Help Prevent a CP4.2 Failure

SPELAB CP4.2 Bypass Kit can't stop the CP4.2 from failing, but it reroutes fuel flow leaving the pump so that—in the event of a failure—you're not buying fuel rails, lines, and an expensive set of piezo injectors on top of replacing the CP4.2.

The CP4 pump is internally lubricated by diesel fuel from the tank. After lubricating the crankcase area of the CP4 pump, fuel enters the high pressure pumping chambers and exits under pressure to the fuel rails and fuel injectors. The weakness of the CP4 pump lies in the crankcase area where a set of roller lifters ride on a camshaft. When the failure event occurs the lubricating fuel becomes contaminated immediately. Our bypass kit mounts to the CP4 pump and changes the routing of the fuel flow so that lubricating fuel from the crankcase is directed back to the fuel tank to be filtered before going through the fuel system again. Thus all fuel entering the pumping elements of the CP4 pump and leaving for the injectors is always routed through both of the vehicle's fuel filters to eliminate any change of contamination from a high pressure pump failure.

This one-time investment could easily save you over $9,000 in repairs and weeks of downtime. It is an absolute must for any 6.7L Power Stroke owner!

The Bosch CP4.2 High-Pressure Fuel Pump Ford 6.7L Power Stroke Engine

Proper maintenance goes a long way, too. This is especially true on all modern-day common-rail diesel engines. Regular fuel filter changes (every other oil change is good practice) and fully priming the fuel system prior to starting the engine after those filter changes is the best way to guard against air infiltrating the high-pressure system. Note that all 6.7L Fords are equipped with a frame-mounted primary filter as well as a secondary filter located up on the engine. As for ensuring that only quality, clean fuel makes it into your tank, fill up at high-traffic filling stations that are regularly being resupplied with fresh diesel.

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