Injection Pressure Control

Fuel Injection Components:

The system uses hydraulically actuated injectors to pressurize the fuel inside the injectors. The hydraulic fluid, used to actuate the injectors, is engine oil.

Oil is drawn from the oil pan through the pickup tube by the engine oil pump. The engine oil pump is a gerotor-type pump driven by the crankshaft. Oil is fed through passages in the front cover to an oil reservoir mounted on top of the cover.

The reservoir makes available a constant supply of oil to a high-pressure hydraulic pump mounted in the engine "V". The high-pressure pump is a gear-driven seven-plunger swash plate pump. High-pressure oil is delivered by the high-pressure pump to oil rails machined into the cylinder heads.

When an injector is electrically energized, a poppet valve is opened by an electronic solenoid mounted on the injector. Oil pressure is allowed to flow into the injector and act on the amplifier piston. When injection is ended, the pressure on top of the amplifier piston is vented by the poppet valve through the top portion of the injector and directed by the oil troughs mounted on the injector to a push tube hole for return to sump.

Injection Pressure Regulator:

Pressure control in the injector control pressure system is closed loop. It is controlled by the Injection Pressure Regulator (IPR) valve, the Injection Control Pressure (ICP) sensor and the strategy in the Powertrain Control Module (PCM).

The pressure regulator valve is a pulse-width modulated valve operating at 400 Hz. The pulse width is modulated from a duty cycle of 8 to 60% to control ICP pressure from 3448-20685 kPa (500-3000 psi). The regulator valve is mounted in the high-pressure pump and achieves injection control pressure regulation by discharging excess oil through a shuttle valve into the front cover and back to sump.

Electronic Components:

The PCM controls the IPR valve by an internal ground switch (low side driver) internal to the PCM. Pressure control is a variable function of the engine control strategy and the calibration that has been programmed into the PCM.

The ICP sensor is mounted on the left cylinder head and is the feedback signal for the closed loop control system. The ICP sensor is a ceramic disk-type pressure sensor that converts pressure into a 0 to 5 volt analog signal that the PCM uses to determine injection control pressure. Typical operating range is 0.7 to 3.2 volts.

A spring/piston pop-off valve is installed internal to the high-pressure pump and is set to discharge oil pressure into the front cover in the event ICP pressure exceeds 27580 kPa (4000 psi).