Engine International VT365. Manual — part 8

ENGINE SYSTEMS

29

Fuel injector operation

The injection operation has three stages:

•

Fill stage

•

Main injection

•

End of main injection

Fill stage

During the fill stage both coils are de-energized and
the spool valve is closed. High pressure oil from the
high pressure oil rail is dead headed at the spool valve.

Low pressure fuel fills the port below the plunger. The
needle control spring holds the needle on its seat to
prevent fuel from entering the combustion chamber.

Main injection (Step 1)

A pulse width current energizes the OPEN coil.
Magnetic force moves the spool open. High-pressure
oil flows past the spool valve into the intensifier piston
chamber. Oil pressure overcomes the force of the
intensifier piston spring and the intensifier starts to
move. An increase in fuel pressure under the plunger
seats the fuel inlet check ball. Fuel pressure starts to
build once the plunger passes the fuel spill port of the
barrel. Force on the needle begins to build.

Main injection (Step 2)

The pulse width controlled current to the OPEN coil
is shut off, but the spool valve remains open. High
pressure oil from high-pressure oil rail continues to
flow past the spool valve. The intensifier piston and
plunger continue to move and fuel pressure increases
in the barrel. When fuel pressure rises above the VOP
- about 21 MPa (3100 psi) - the needle lifts of its seat
and injection begins.

End of main injection (Step 1)

When the Injector Drive Module (IDM) determines
that the correct injector On Time has been reached
(meaning the correct amount of fuel has been
delivered), the IDM sends pulse width controlled
current to the CLOSE coil of the injector. The current
energizes the CLOSE coil and magnetic force closes
the spool valve. High pressure oil is dead headed
against the spool valve.

End of main injection (Step 2)

The pulse width controlled current to the CLOSE
coil is shut off, but the spool valve remains closed.
The intensifier piston and plunger return to their initial
position. Oil above the intensifier piston flows past the
spool valve through the exhaust ports. Fuel pressure
decreases until the needle control spring forces the
needle back onto its seat.

30

ENGINE SYSTEMS

Fuel Supply System

Figure 25 Fuel supply system

1.

Fuel injector assembly (8)

2.

Plug assembly, fuel rail (2)

3.

Cylinder head (right)

4.

Fuel supply line (right cylinder
head)

5.

Fuel supply line (left cylinder
head)

6.

Cylinder head (left)

7.

12 mm banjo bolt with check
valve (2)

8.

Fuel filter housing assembly

9.

Fuel filter regulator valve
assembly

10. Fuel and power steering pump

assembly (gear driven)

11. Fuel filter prestrainer

12. Fuel filter water drain tube

assembly

13. Fuel supply line
14. Fuel return line

ENGINE SYSTEMS

31

Figure 26

Fuel system schematic

The fuel supply system includes the following:

•

Check valve banjo bolts

•

Fuel tank(s)

•

Fuel filter and housing

•

Fuel supply lines

•

Fuel passages in cylinder heads

•

Fuel pressure regulator and fuel return lines

•

Fuel supply pump (transfer)

Fuel Flow

The fuel pump draws fuel from the fuel tank(s). Fuel
passes through an 80 micron strainer on the pump.
The fuel pump pressurizes and transfers fuel to the
base of the fuel filter housing.

•

The fuel filter housing regulates fuel pressure
and relieves excessive pressure back to the fuel
tank(s) through a fuel line connected to the top of
the fuel filter housing. The fuel pressure regulator
is calibrated to open at 345 kPa (50 psi) but at
high rpm, low load pressure could reach more
than 517 kPa (75 psi).

32

ENGINE SYSTEMS

•

The fuel is conditioned as it passes through a 10
micron filter to a standpipe in the center of the fuel
filter housing.

•

An optional electric heating element in the fuel
filter housing warms the fuel to prevent waxing.

•

A sensor in the base of the fuel housing
detects water in the fuel. When enough water
accumulates in the bottom of the housing, the
sensor sends a signal to light the optional Water
In Fuel (WIF) lamp on the instrument panel.

•

A fuel drain valve on the housing is used to
eliminate contaminants (usually water) from the
fuel housing.

•

Filtered fuel flows from the fuel filter housing to
both cylinder heads through fuel lines.

Fuel flows past check valves through passages in the
cylinder heads that intersect with the fuel injectors.