User Manual

The primary fuel filter/water separator will not trap these small contaminants. Very small abrasive particles in
the fuel cause abrasive deterioration of the unit injectors. The secondary fuel filter removes particles in the size
of two microns in size or particles that are greater than two microns in size. The use and regular maintenance of
this two micron filter will provide a significant improvement in injector life.
Fuel flows from the two micron secondary filter to the fuel supply passage in the cylinder head. The fuel supply
passage is a drilled hole which begins at the front of the cylinder head. The fuel supply passage extends to the
back of the cylinder head. This passage connects with each unit injector bore in order to supply fuel to unit
injectors. The excess fuel flows out of the back of the cylinder head. The fuel flows into the fuel pressure
regulator.
The fuel pressure regulator consists of an orifice and a check valve that is spring loaded. The orifice is a flow
restriction that pressurizes the supply fuel. The check valve that is spring loaded will open at 35 kPa (5 psi) in
order to allow the fuel that has flowed through the orifice to return to the fuel tank. When the engine is off, there
is no fuel pressure that is acting on the check valve. With no fuel pressure on the check valve, the check valve
will close. The check valve will close in order to prevent the fuel that is in the cylinder head from draining back
to the fuel tank.
Injection Actuation System
Actuation Oil Flow
(1) Unit injector hydraulic pump
(8) Oil filter
(9) Oil cooler
(10) Engine oil pump
(11) High pressure oil
The injection actuation system serves two
functions. The injection actuation system
supplies high pressure oil in order to
power the injectors. Also, the injection
actuation system regulates the injection
pressure that is produced by the unit
injectors by changing the actuation
pressure of the oil.
The injection actuation system consists of four basic components:
• Engine oil pump
• Engine oil filter
• Unit injector hydraulic pump
• Injection actuation pressure sensor (IAP Sensor)