What causes a diesel engine to hunt?

Answer 1

A diesel engine "hunting" refers to a fluctuation in engine speed or RPM. This can be caused by issues such as a dirty or clogged fuel filter, air in the fuel system, a malfunctioning fuel injection system, incorrect fuel injection timing, or a faulty engine sensor. These issues can disrupt the proper combustion process in the engine, leading to the hunting behavior.

Answer 2

"Hunting" is the term generally applied to an engine that will not maintain a constant speed with a fixed throttle setting. Most modern engines with electronic feedback controls do no have this problem. It is usually found in older diesels that use a "governor" to control speed. The governor is a centrifugal weight system that applies force to a spring-loaded fuel flow control. Hunting is caused when the linkages become worn and sloppy, causing a variable relationship between engine speed and fuel feed rate.