(3) Position the new pressure solenoid horizontally
into the high pressure injection pump, twist slightly
while pressing into pump. Ensure the mating sur-
faces of both components are flush (Fig. 2).
(4) Install the pressure solenoid retaining screws
by hand and tighten in 2 phases. 3 - 4Nm (27 -
35lbs.in.) then 6 - 7Nm (53 - 62 lbs.in.).
(5) Connect the pressure solenoid electrical connec-
tor.
(6) Install the power steering resivior into it’s
mounting bracket.
(7) Connect the negative battery cable.
(8) Perform the Fuel System Air Purge procedure
(Refer to 14 - FUEL SYSTEM - STANDARD PROCE-
DURE).
FUEL INJECTOR
DESCRIPTION
FUEL INJECTOR
WARNING: HIGH - PRESSURE FUEL LINE DELIVER
DIESEL FUEL UNDER EXTREME PRESSURE FROM
THE INJECTION PUMP TO THE FUEL INJECTORS.
THIS MAY BE AS HIGH AS 1600BAR (23,200PSI).
USE EXTREME CAUTION WHEN INSPECTING FOR
HIGH - PRESSURE FUEL LEAKS. FUEL UNDER
THIS AMOUNT OF PRESSURE CAN PENETRATE
SKIN CAUSING PERSONAL INJURY OR DEATH.
INSPECT FOR HIGH - PRESSURE LEAKS WITH A
SHEET OF CARDBOARD. WEAR SAFETY GOG-
GLES AND ADEQUATE PROTECTIVE CLOTHING
WHEN SERVICING FUEL SYSTEM.
(Refer to 14 - FUEL SYSTEM - WARNING) There
are individual fuel injectors for all four cylinders.
These fuel injectors are used to spray fuel into the
combustion chamber (Fig. 3).
OPERATION
(Refer to 14 - FUEL SYSTEM - WARNING) The
injector operation can be subdivided into four operat-
ing states with the engine running and the high-
pressure pump generating pressure:
• Injector closed (with high pressure applied)
• Injector opens (start of injection)
• Injector opened fully
• Injector closes (end of injection)
Injector closed (with high pressure applied)
With the injector closed (at-rest state), the solenoid
valve is not energized and is therefore closed. With
the bleed orifice closed, the valve spring forces the
armature’s ball onto the bleed-orifice seat. The rail’s
high pressure build up in the valve control chamber,
and the same pressure is also present in the nozzle’s
chamber volume. The rail pressure applied at the
control plunger’s end face, together with the force of
the nozzle spring, maintain the nozzle in the closed
position against the opening forces applied to its
pressure stage (Fig. 4).
Injector opens (start of injection)
The solenoid valve is energized with the pickup
current which serves to ensure that it open quickly.
The force exerted by the triggered solenoid now
exceeds that of the valve spring and the armature
opens the bleed orifice. Almost immediately, the high-
level pick-up current is reduced to the lower holding
current required for the electromagnet. This is possi-
ble due to the magnetic circuit’s air gap now being
smaller. When the bleed orifice opens, fuel can flow
from the valve control chamber into the cavity situ-
ated above it, and from there via the fuel return to
the tank. The bleed orifice prevents complete pres-
sure balance, and the pressure in the valve control
chamber sinks as a result. This leads to the pressure
in the valve-control chamber being lower than that in
the nozzle’s chamber volume which is still at the
same pressure level as the rail. The reduced pressure
in the valve-control chamber causes a reduction in
the force exerted on the control plunger, the nozzle
needle open as a result, and injection starts (Fig. 4).
Fig. 3 FUEL INJECTOR
1 - FUEL INJECTOR
2 - NOZZLE
3 - FUEL INLET FITTING
4 - ELECTRICAL CONNECTION
RG
FUEL INJECTION
14 - 19
FUEL PRESSURE SOLENOID (Continued)