The 6.7L Power Stroke uses the Bosch CP4.2 high-pressure fuel pump. It is efficient and quiet, but like other CP4 applications it can fail catastrophically and take the entire fuel system with it. If you own a 6.7L Power Stroke, this is a failure mode worth understanding before it happens.
What actually fails
The CP4.2 relies on diesel fuel for internal lubrication. If it runs low on lubrication or ingests air, an internal roller follower can rotate out of its track and score the pump. Fine metal debris is then pumped downstream at extreme pressure into the rails, lines, and injectors. What started as a pump problem becomes a full fuel-system contamination event.
Symptoms
- Sudden power loss, often followed by a no-start
- Rail-pressure and fuel-system fault codes
- Metal glitter in the fuel filter housing
- Rough running just before total failure
Why it is so expensive
Because debris spreads through the whole high-pressure side, a true CP4 failure usually means replacing the pump, both rails, the high-pressure lines, and all eight injectors, plus a thorough flush. That is why the repair frequently lands in five figures. Catching it the instant power drops, before you crank repeatedly, can limit the spread.
Prevention
Two popular strategies reduce the risk. A disaster-prevention (bypass) kit reroutes and filters fuel so that if the pump does fail, debris is far less likely to reach the injectors. Alternatively, a CP3 conversion replaces the CP4.2 with the older, more robust CP3 that does not fail the same way. On top of either, keep fuel clean, never run the tank dry, and change fuel filters on schedule.
Frequently asked questions
Can I prevent a CP4 failure?
You can greatly reduce the risk with a disaster-prevention kit or a CP3 conversion, plus disciplined fuel filtration and never running low on fuel.
What does a CP4 failure cost to fix?
Because it contaminates the rails, lines, and injectors, a full repair commonly runs well into five figures.
Is the CP3 swap legal and reliable?
The CP3 is a proven, robust pump. Many owners convert for reliability; confirm compliance for your area before modifying emissions-related hardware.
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