User Manual

Pilot Injection
Cross section of pilot injection cycle
(1) Solenoid
(3) Armature
(4) Seated pin
(6) Spool valve
(7) Check ball for intensifier piston
(8) Intensifier piston
(10) Plunger
(15) Nozzle spring
(16) Check piston
(19) Nozzle check
(20) Nozzle tip
(21) Drain
Pilot injection occurs when the ECM sends a
control current to the solenoid (1) . The current
creates a magnetic field which lifts the armature
(3) and the seated pin (4) . The seated pin has a
lower seat and an upper seat. When the seated pin
is lifted by the armature, the upper seat closes off
the flow of actuation pressure to the check. The
lower seat opens. This allows the actuation oil on
top of check piston (16) to flow to drain (21) .
Actuation oil that is trapped below spool (6) will
also flow to drain (21) . The actuation oil drains
through a vent hole in the side of the injector.
The drop in pressure under the spool causes a
hydraulic difference that acts on the spool. The
spool moves into the open position when
hydraulic pressure acts on the top of the spool.
This hydraulic pressure forces the spool
downward. The downward movement of the spool
is stopped when the spool and the pin force the
check ball (7) for the intensifier piston onto the
ball seat in the closed position. This prevents any actuation pressure from escaping from the cavity for the
intensifier piston (8) . This drop in the actuation pressure also removes the downward force on the check piston.