TL960 SERVICE MANUAL
The upward force from the pressurized fuel almost instantly becomes greater than the downward force on the intensifier so the downward motion of the intensifier and plunger stops. When the plunger stops, fuel flow also stops. With the check still open, the remaining pressure on the fuel pushes a tiny amount of additional fuel out the orifice holes. This causes a large pressure drop which lowers nozzle pressure below Valve Closing Pressure (VCP) of 3,200 psi. Spring tension on the check then reseats the check and injection stops.
Fill Cycle When the check closes, injection stops and the fill cycle starts as follows: The poppet and intensifier cavities are open to atmospheric pressure through the poppet valve and adapter drain hole. Pressure drops very rapidly in the intensifier and plunger cavities to near zero.