To kick things off, we’re going to look at something that’s very near and dear to our hearts: the CP4 injection pump on 2011-present LML Duramax engines. Boy, where to begin? People have taken a somewhat hyperbolic approach and refer to the CP4 as a time bomb, among other colorful terms. The thing is, they’re not too far from the truth. Even if you have a 100 percent stock pickup, there’s a [really] good chance that you’re going to be on the receiving end of a $10,000 bill when it finally goes out on you and destroys your entire fuel system.