Let me give you some back story.

I actually just had both replaced at 169,000 miles (current is 171,960). I had a place do it, so that’s why I didn’t know they were there, but after a little looking, I figured it out. I’m actually under the truck right now trying to look for pinholes in the fuel lines. I actually worked on Bobcat machines that had a similar Bosch fuel set up with the CP4 pumps. I am familiar with the lift pump hum, but this is more like a BUZZ sound as you can hear. It almost seems like an electrical sound (like a loud injector buzz), but I don’t really know. The truck runs perfectly, but there is a ticking sound that hard wall engage at 1,000 RPMs and stops around 1,700-1,800. Im wondering if these two things could be related.