Mechanical diesel injection pumps are actually all governor controlled. The throttle is actually controlling the setting of the speed governor, (sometimes called a "speed regulator") which in turn controls the volume of fuel delivered by the injection pump to deliver the amount of fuel needed to run the engine at the commanded speed.
On Bosch injections systems (like on the Volvo) the governor/regulator is internal to the injector pump, and like all the internal parts of the injection pump, it tends to be highly reliable. But if an engine can not control its speed under no load, it is a likely candidate for a problem.
On some engines the governor is a separate device. I did once work on an engine that had a separate governor that was badly clogged up with emulsified oil when water got into the crankcase... a very unhappy story...
Palmetto Point, Eleuthera, Bahamas
---In amelyachtowners@..., <ianjudyjenkins@...> wrote :
Do you have the 78hp Volvo with a governor ? Can you tell me how the governor works--and what might upset it ?