Fuel Injectors - International VT 365 Service Manual

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Fuel Injectors

Figure 24 Fuel Injector
1. CLOSE coil
2. Control valve body
3. Intensifier piston
4. Piston return spring
5. Plunger
6. Valve opening pressure spring
7. Needle
8. OPEN coil
9. Spool valve (control valve)
10. Casenut
11. Fuel strainer (3)
12. Nozzle assembly
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
ENGINE SYSTEMS
Fuel injector features
Two 48 volt 20 amp coils control a spool valve that
directs oil flow in and out of the injector. The injector
coils are turned on for approximately 800 (micro
second or millionth of a second). Each injector has
a single four pin connector that passes through the
rocker arm carrier
Injector coils and spool valve
An OPEN coil and a CLOSE coil on the injector move
the spool from side to side using magnetic force. The
spool has two positions:
•
•
Intensifier piston
When the spool valve is open, high pressure oil
enters the injector, pushing down the intensifier piston
and plunger. Since the intensifier piston is 7.1 times
greater in surface area than the plunger, the injection
pressure is also 7.1 times greater than ICP pressure
on the plunger.
Plunger and barrel
Fuel pressure builds between the plunger and the
barrel. When the intensifier piston pushes the plunger
down, the plunger increases fuel pressure in the
barrel 7.1 times greater than ICP. The plunger has
tungsten carbide coating to reduce scuffing and poor
performance.
Injector needle
The injector needle opens inward, off its seat when
fuel pressure overcomes the Valve Opening Pressure
(VOP) - approximately 21 MPa (3100 psi). Fuel is
atomized at high pressure through the nozzle tip.
EGES295-2
Follow all warnings, cautions, and notes.
© 2006 International Truck and Engine Corporation
When the spool valve is open oil flows into the
injector from the high pressure oil rail.
When the spool valve is closed oil drains back to
the crankcase.