Fuel Charging and Controls

Part 1 Of 2:

Part 2 Of 2:

The fuel system used on the Direct Injection (DI) turbo diesel engine is controlled by the Powertrain Control Module (PCM).

The fuel system components consist of:
^ electric inline fuel pump.
^ high-pressure oil pump.
^ fuel filter.
^ oil pressure regulator.
^ oil pressure sensor.
^ fuel pressure regulator.
^ high-pressure oil pump reservoir.
^ water in fuel switch/fuel heater thermostat.

Fuel is drawn from the fuel tank by the electric fuel pump. The fuel is then supplied under low pressure, 310-448 kPa (45-65 psi), to the fuel filter/water separator assembly.

Fuel to be supplied to the combustion chambers passes through the fuel filter/water separator assembly into the cylinder head galleries, then through the hydraulically actuated/electronically controlled fuel injectors.

Excess fuel not used by the engine bypasses the fuel filter/water separator assembly, flows through the fuel pressure regulator assembly, and returns to the fuel tank.

Fuel Pump
The fuel pump is an in-line electric pump mounted on the left hand frame rail. The fuel pump draws fuel from the fuel tank and supplies it to the engine at 310-448 kPa (45-65 psi).

Fuel Filter/Water Separator
The diesel engine is equipped with a fuel filter and water separator assembly. Drain the water from the fuel filter at the recommended maintenance intervals. Refer to Maintenance for the maintenance intervals.
A water in fuel indicator on the instrument panel will alert the operator. When the indicator glows continuously while the engine is running, drain the water from the fuel filter and water separator bowl as soon as possible to prevent damage to the fuel injection system; refer to Fuel Filter Water Draining. Fuel/Water Separator






















The unit injector is composed of five major components: The electronic solenoid, the poppet valve, the amplifier piston, the fuel plunger and the nozzle assembly. Operation of the injector is included in the following description.

CAUTION:
^ Color of Service Parts identification clip may differ from color of Production identification clip. Verify identification using part number and parts catalog.
^ Do not interchange fuel injectors. Improper injector installation can cause severe engine damage.

An electronically controlled/hydraulically actuated fuel injector is used. The rate shape fuel injector incorporates a spill control port that helps balance the fuel delivery, reducing the emissions and engine noise.

When the fuel injector is energized, a poppet valve is opened by an electronic solenoid mounted on the fuel injector. High-pressure oil from the high-pressure oil pump flows into the fuel injector and acts on the amplifier piston, forcing the piston plunger downward. As the plunger moves down, the increased fuel pressure closes the fuel inlet check ball. Rising fuel pressure overcomes spring pressure and opens the nozzle check valve. Fuel is then injected into the combustion chamber through the eight spray orifices in the nozzle tip at pressures as high as 124, 110 kPa (18,000 psi). When the fuel injector is de-energized, high-pressure oil on top of the amplifier piston is vented by the poppet valve through the top portion of the fuel injector back to the oil pan.

HIGH PRESSURE OIL SYSTEM







The 7.3L Powerstroke diesel injectors are powered by lubricating oil which is pressurized by a swashplate pump (Rexroth pump) in the engine valley. The pump output pressure ranges from 3,102 to 20,685 kPa (450 psi to 3,000 psi). Oil pressure is controlled by the Powertrain Control Module (PCM) through the Injector Pressure Regulator (IPR) Valve. The PCM controls pressure in the oil rail by opening (relieving pressure) and closing (increasing pressure) the IPR valve. The high pressure oil is delivered to oil rails in the cylinder heads. An Injection Control Pressure sensor mounted on one of the oil rails sends an analog voltage signal (0.5 V to 5.0 V) to the PCM for feedback control of the oil pressure.

UNIT INJECTOR AMPLIFIER PISTON
The high pressure oil flows from the oil rails into an amplifier piston located in the injector. Oil entry and exit to and from the amplifier piston is controlled by a solenoid-operated poppet valve.

UNIT INJECTOR FUEL PLUNGER
The fuel plunger is located in the injector and is driven by the amplifier piston. The fuel plunger injects fuel into the combustion chamber at pressures of up to 144,795 kPa (21,000 psi) through the nozzle assembly. Fuel is supplied to the injector at approximately 483 kPa (50-70 psi) through fuel rails in the cylinder heads.

INJECTOR DRIVER MODULE
The solenoid-operated poppet valve requires 115 volts at up to 8 amps to operate, which is more power than the PCM can supply. Therefore, a high power device, the Injector Driver Module, is used to supply power to the solenoid on command from the PCM.

PCM CONTROL OF FUEL INJECTION
The command signal from the PCM to the Injection Driver Module is the Fuel Delivery Control Signal. The poppet valve requires 12 volts to command the poppet open and 0 volts to command the poppet closed. The PCM also supplies a synchronizing signal, CMP, to indicate cylinder No. 1 (going from 0 to 12 volts) and cylinder No. 4 (fires 5th) (going from 12 to 0 volts).

ENGINE TIMING
The PCM controls both duration and timing of the injection event with the fuel delivery control signal. Signal duration, or fuel pulse width, is shown as Parameter ID (PID) "FUEL_PW" on the New Generation Star (NGS) Tester.

The PCM controls the fuel plunger injection pressure and fuel volume by varying the injection oil pressure with the Injection Pressure Regulator. The command to the Injection Pressure Regulator is a 12 volt, Pulse Width Modulated (PWM) signal (controlled on the ground side).

The injection oil pressure command is shown as NGS PID IPR which is the percentage ON of the pulse width modulated signal. Injection oil pressure is shown as NGS PID ICP.

The PCM receives engine rotational position information from the Camshaft Position sensor (CMP). The CMP is a hall-effect device. It outputs 12 volts to the PCM whenever it detects the iron of a spoked target wheel in front of it, and it outputs 0 volts whenever it detects the space between the spokes. The target wheel spokes and spaces are each 15 crank degrees, except for narrow spoke which indicates cylinder No. 1 and a wide spoke which indicates cylinder No. 4 (fires 5th). The NGS PID RPM is generated by the PCM from the CMP signal.

FUELING CORRECTIONS
The PCM adjusts injector output based on oil temperature information received from the Engine Oil Temperature sensor and turbo boost information received from the Manifold Absolute Pressure (MAP) Sensor, and the Barometric pressure (BARO) sensor. These corrections are necessary to meet emissions requirements and to optimize power. Outputs of these sensors are displayed on the NGS tester as EOT (temperature), MAP (boost pressure), BARO (pressure), and BARO V (volts). MGP shows boost.

Fuel Pressure Regulator
Fuel pressure in the cylinder head fuel galleries is maintained at 310-448 kPa (45-65 psi) by a fuel pressure regulator. The fuel pressure regulator consist of a spring-loaded poppet valve, which opens to allow excess fuel to exit fuel filter/water separator prior to being cycled through the fuel filter. Fuel exiting the fuel filter/water separator is returned to the fuel tank.







Oil Pressure Regulator
Fuel injection pressure is controlled by the Injection Control Pressure (ICP) system. The ICP system consists of:
^ injection control pressure (ICP) sensor (located in the cylinder head oil gallery)
^ Injection Pressure Regulator (IPR) located in the high-pressure oil pump
^ powertrain control module

Fuel Charging Wiring
The fuel charging wiring connects the engine wire harness to each fuel injector and engine controls such as the injection control pressure (ICP) sensor, injection pressure regulator (IPR) and injector driver module (IDM). The fuel charging wiring receives fuel injector signals from the powertrain control module and the injector driver module then transfers the signals to the fuel injectors.