Fuel Charging and Controls
Fuel Charging and Controls
System Cleanliness
The common rail fuel injection system consists of components manufactured to precise tolerances. It is critical to make sure of absolute cleanliness during all servicing of the common rail fuel injection system. Attention to cleanliness must also be followed when storing and handling parts. Use of lint-free rags is required while servicing the fuel system. Clean high-pressure joints and surrounding area before removing any high-pressure tube or components. Fuel System Caps must be used when any high-pressure fuel tube is serviced. Make sure system components and joints are clean prior to assembly.
Fuel System
WARNING: Avoid contact with fuel during a visual inspection for fuel leaks with the engine running. Do not work on the fuel system until the pressure has been released and the engine has cooled. Fuel in the high-pressure fuel system is hot and under very high pressure. High-pressure fuel may cause cuts and contact with hot fuel may cause burns. Failure to follow these instructions may result in serious personal injury.
NOTICE: Before disconnecting any part of the fuel system, it is important that all dust, dirt and foreign material is removed from around components to prevent ingress of foreign matter into the fuel system or the vehicle may be damaged.
NOTICE: The fuel tubes between the pump and the fuel rail, and the fuel rail and the injectors, must be discarded after each use and new tubes installed or the vehicle may be damaged.
NOTICE: It is essential that absolute cleanliness is observed when working with these components. Always install Fuel System Caps to any open orifice or tubes, or the vehicle may be damaged.
NOTICE: Make sure that the workshop area in which the vehicle being worked on is as clean and dust-free as possible. Areas in which work on clutches, brakes or where welding or machining are carried out are not suitable due to the risk of contamination to the fuel system. Failure to follow this instruction may result in damage to the vehicle.
NOTICE: Use a steel-topped work bench or cover it with clean, lint-free, non-flocking material. Failure to follow this instruction may result in damage to the vehicle.
NOTICE: Do not attempt to apply battery voltage to the fuel injector or damage to the fuel injector will occur.
NOTICE: Use only banjo bolts with a green hex head. Failure to install the correct banjo bolt may result in damage to the fuel system.
The high-pressure common rail fuel system used on the 6.4L direct injection turbocharged diesel engine is controlled electronically by the PCM. The high-pressure fuel is delivered by the use of piezo-actuated fuel injectors.
The fuel system components consist of the following:
- Engine fuel filter module
- High-pressure fuel injection pump
- Pressure control valve (serviced with pump assembly)
- Volume control valve (serviced with pump assembly)
- High-pressure fuel rail
- Fuel Rail Pressure (FRP) sensor
- Piezo-actuated fuel injectors
- High-pressure fuel tubes
- Fuel injector and high-pressure fuel injection pump fuel return tubes and check valve
Fuel to be supplied to the combustion chamber passes through the horizontal fuel conditioning module into the engine fuel filter module. The low-pressure filtered fuel enters the high-pressure fuel injection pump, which is then transferred to and stored in the fuel rails. The PCM-controlled, high-pressure fuel injection pump generates pressures up to 170 kPa (24,650 psi) at rated horsepower. The storage of high-pressure fuel makes it possible to provide a constant injection pressure regardless of the quantity of fuel required or the engine speed. The injection parameters are:
- Injection pressure
- Number of injections
- Timing of injections
- Injection quantity
These parameters are utilized for each injection phase within the piston cycle. This system uses pre-injection (pilot), main-injection and post-injection to meet engine operating criteria:
- Engine system emissions
- Combustion noise reduction
- Engine performance
High-Pressure Fuel System Flow
- Fuel is sent to the high-pressure fuel injection pump via the horizontal fuel conditioning module and fuel filter module, which filters the fuel.
- The high-pressure fuel injection pump is gear driven by the camshaft gear at the rear of the engine.
- Once the high-pressure fuel injection pump pressurizes the fuel it is routed to 2 steel tubes, one for each bank.
- The steel tubes route the fuel to the high-pressure fuel rail via a fitting that extends through the valve cover carrier.
- The high-pressure fuel rail routes fuel to each of the 4 injectors via 4 separate steel fuel tubes.
High-Pressure Fuel Injection Pump
The high-pressure fuel injection pump is mounted in the rear of the engine valley and is driven by the camshaft gear. The high-pressure fuel injection pump is serviced as an assembly only. The high-pressure fuel injection pump gear is fastened to the pump and fastened using a LH-threaded fastener.
Piezo Actuated Fuel Injector
- The injector has a replaceable O-ring seal on the outside of the body and a replaceable soft steel combustion gasket on the tip of the injector.
- The injector's piezo actuator has a 2-pin connector that is located under the valve cover.
- The fuel charging wiring harness has a single main connection point at the front of the valve cover base.
The injectors are controlled by the PCM via an internal injector driver. The fuel injectors are electrically connected to the PCM via the fuel charging wiring harness located under the valve cover. The fuel charging wiring harness is candy striped to provide a visual identification of high voltage, 80 to 200V. The injectors use a piezo actuator instead of a solenoid to control injection. The piezo actuator provides an accurate control of injection timing and quantity per piston cycle. The fuel injectors contain 6 orifices that provide an extremely fine fuel spray into the combustion chamber. The PCM controlled fuel injector injects fuel into the combustion chamber at pressures up to 170 kPa (24,650 psi) at rated horsepower. Handle components with extreme care when servicing.
The fuel injector fits into a sleeved bore machined into the cylinder head. The injector bore intersects with a machined fuel return passage that runs the length of the cylinder head. Low-pressure fuel return from the injectors flows through the cylinder head passage and joins the high-pressure fuel injection pump-to-fuel cooler return tube in the valley of the engine. The fuel return travels through the engine fuel cooler, to reduce fuel temperature to the fuel filter module, where the fuel is filtered and returned to the high-pressure injection pump or returned back to the fuel tank (depending on engine demand). Each injector contains an O-ring seal around the outer body, above the fuel passage. All injectors have a combustion gasket to seal combustion gases from entering the fuel return passage or the crankcase and to prevent fuel from entering the crankcase.
High-Pressure Fuel Pump Cover and Gasket
The high-pressure fuel injection pump cover fastens to the engine block at the rear of the engine valley. There are 2 gaskets, the upper and the lower pump cover gaskets. The upper pump cover gasket seals the pump cover to the top of the pump. The lower gasket, which contains an integrated electrical harness to support the pressure control valve and the volume control valve, seals the pump cover to the cylinder block and rear cover. When removing the fuel pump cover, always install new upper and lower gaskets. After removing the high-pressure fuel tubes, it is crucial that the Fuel System Caps are installed on the high-pressure pump ports. When reassembling the pump cover, make sure the upper gasket is located in the pump cover groove. RTV Silicone Sealant TA-31 must be correctly applied to the engine block-to-rear cover junctions (2 locations) when assembling the lower pump cover gasket. Visually inspect the wire routing of the lower gasket integrated circuit to make sure that the wires do not overlay the sealing bead during assembly.