Injection Timing Device: Notes
With the distributor injection pump stopped, a pre-loaded injection timing spring holds the injection timing piston in starting position. The pressure control valve, in conjunction with the spill orifice, keeps the fuel pressure in the pump's inside chamber proportional to the engine speed during operation of pump. See Fig 1.
From a certain speed the inside chamber pressure will be greater than the spring force and move the injection timing piston. The axial piston motion is transmitted by a slide and pin to the rotating roller ring. This changes the arrangement between cam and the roller ring so that the turning cam will be lifted to advanced timing by the rollers of the roller ring. This means that the position of the distributor piston in regards to rotary movement compared with the crankshaft or camshaft is displaced by a defined angle.