Electronic Control System - Perkins 1104D NH1 Systems Operation Testing And Adjusting

RENR7967
Fuel Injectors
Illustration 28
The fuel injectors are not serviceable.
When the ECM sends a signal to the injector
solenoid, a valve inside the injector opens. The valve
allows the high pressure fuel from the fuel manifold
to enter the injector. The pressure of the fuel pushes
the needle valve and a spring. When the force of the
fuel pressure is greater than the force of the spring,
the needle valve will lift up.
The timing and duration of injection is controlled by
a solenoid valve in the injector. The valve has two
positions. In the closed position, the valve closes the
inlet to the injector. In this position, fuel above the
injector needle is allowed to vent through the leakoff
port.
In the open position, the valve opens the inlet to the
injector. Simultaneously, the valve closes the leakoff
port in order to allow high pressure fuel to flow to the
needle. When the solenoid valve is closed, some fuel
escapes past the valve in order to vent through the
leakoff port. A certain volume of fuel always flows
from the leakoff port. If the volume of fuel increases
beyond a critical level, the high pressure fuel pump
will not be able to maintain pressure in the fuel
manifold. The faulty electronic unit injector must be
identified and replaced.
When the signal to the injector ends, the valve closes.
The fuel in the injector changes to a low pressure.
When the pressure drops the needle valve will close
and the injection cycle stops. When the needle valve
opens, fuel under high pressure will flow through
nozzle orifices into the cylinder. The fuel is injected
into the cylinder through the orifices in the nozzle as
a very fine spray.
The needle valve has a close fit with the inside of the
nozzle. This makes a positive seal for the valve.
Fuel Manifold
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Illustration 29
Typical example
The fuel manifold (1) stores high pressure fuel from
the fuel injection pump. The high pressure fuel will
flow to the injectors.
The fuel pressure sensor (2) measures the fuel
pressure in the fuel manifold (1).
The relief valve (3) will prevent the fuel pressure from
getting too high.

Electronic Control System

Introduction (Electronic Control
System)
The ECM and the sensors are located on the left side
of the engine. Refer to illustration 30.
Systems Operation Section
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