Knock, Knock.  Fuel System Calling.

There's probably nothing more critical to maximum fuel performance and engine longevity than clean, uncontaminated fuel. Without regular fuel system maintenance and high-quality fuel filtration, you may face engine downtime as well as costly repairs. If you're having problems with equipment knocking, vibrating excessively, lacking in power, smoking, operating erratically, losing fuel, or not starting at all, it may be because you're giving too little attention to fuel system maintenance. It's important to understand why fuel systems should be so high on your maintenance priority list. Diesel engines have evolved dramatically over recent decades