C7 Industrial Engines Systems Operation – Fuel System

Main Injection

Cross section of main injection cycle

(39) Solenoid

(41) Armature

(42) Seated pin

(44) Spool valve

(45) Check ball for intensifier piston

(54) Check piston

(57) Nozzle check

(60) Drain

Refer to Illustration 12. Main injection begins when the solenoid (39) is re-energized. The magnetic field is instantly created and the force of the magnetic field lifts the armature (41) and the seated pin (42). The upper seat closes off the flow of actuation pressure and the upper seat opens the check piston (54) and the bottom of the spool (44) to the drain (22). The hydraulic force that holds the nozzle check (57) closed quickly dissipates and the injection pressure opens the nozzle check. This is the start of main injection. A difference in hydraulic forces on the spool is also created. This difference forces the spool downward. The check ball (45) for the intensifier piston is held in the closed position when the spool is in this position. Main injection continues if the solenoid remains energized.

Fill

Illustration 13 g01448518
Cross section of fill cycle

(39) Solenoid

(40) Armature spring

(41) Armature

(42) Seated pin

(43) Spool spring

(44) Spool valve

(45) Check ball for intensifier piston

(46) Intensifier piston

(47) Return spring

(48) Plunger

(54) Check piston

(56) Reverse flow check valve

(57) Nozzle check

Refer to Illustration 13. The fill cycle begins when the solenoid (39) is de-energized. The armature (41) and the seated pin (42) are forced down by the armature spring (40). The seated pin closes the lower seat and the seated pin opens the upper seat. Actuation pressure is restored to the top of the check piston (54). This closes the nozzle check (57) and injection ends. Actuation pressure is also felt under the valve spool (44). This restores the hydraulic balance on the spool. The valve spring (43) slowly closes the spool. This stops the flow of actuation oil to the intensifier piston (48) .

As the spool raises, the check ball (45) for the intensifier piston is no longer held closed. Oil in the cavity for the intensifier piston lifts the check off the seat and flows to the drain (60) through a vent hole in the side of the injector. Return spring (47) pushes up plunger (48) and the intensifier piston. This pushes all of the oil out of the cavity for the intensifier piston. The check valve (56) for the fuel inlet is taken off of the valve seat as the plunger lifts up. This allows supply fuel to flow into the plunger cavity. The fill cycle is complete when the plunger and the piston are at the top of the bore and the plunger cavity is full of fuel.