C7 Industrial Engines Systems Operation – Fuel System

HEUI Injector (Components)

The HEUI injector serves four functions. The HEUI injector pressurizes supply fuel from 450 kPa (65 psi) to 175 MPa (25382 psi). The HEUI injector functions as an atomizer by pumping high pressure fuel through orifice holes in the unit injector tip. The HEUI injector delivers the correct amount of atomized fuel into the combustion chamber and the HEUI injector disperses the atomized fuel evenly throughout the combustion chamber.

Illustration 8 g01448432
Cross section of HEUI injector

(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

(49) Barrel

(50) Nozzle case

(51) Inlet fill check

(52) Stop

(53) Nozzle spring

(54) Check piston

(55) Sleeve

(56) Reverse flow check valve

(57) Nozzle check

(58) Nozzle tip

Refer to Illustration 8. The HEUI injector consists of three major parts:

• Upper end, or actuator (A)
• Middle, or pumping unit (B)
• Lower end, or nozzle assembly (C)

The upper end (A) consists of the following items:

• Solenoid (39)
• Armature spring (40)
• Armature (41)
• Seated pin (42)
• Spool spring (43)
• Spool valve (44)
• Check ball for intensifier piston (45)

The middle of the injector (B) contains the following items:

• Intensifier piston (46)
• Return spring (47)
• Plunger (48)
• Barrel (49)

The lower end of the injector (C) consists of the following items:

• Nozzle case (50)
• Inlet fill check (51)
• Stop (52)
• Nozzle spring (53)
• Check piston (54)
• Sleeve (55)
• Reverse flow check valve (56)
• Nozzle check (57)
• Nozzle tip (58)

These components work together in order to produce different rates for fuel injection. The rates for fuel injection are electronically controlled by performance software in the ECM.