What’s failing: The CP4 pump’s roller‑tappet design struggles with low‑lubricity U.S. diesel fuel, leading to internal wear and metal debris contamination. Who’s affected: GM Duramax (2011–2016), Ford ...

If you browse forums often, chances are you've come across some heated discussions around the CP4 fuel pump. The CP4, short for "Common Rail Pump 4," is a high-pressure fuel injection pump that made ...