Component Description
LOW AND HIGH PRESSURE FUEL LINES
| ITEM | DESCRIPTION |
|---|---|
| A | Low Pressure (LP) fuel line |
| B | High Pressure (HP) fuel line |
| 1 | Heat reflective and insulation sleeve |
| 2 | Acoustic covers |
| 3 | Fuel pipe cover |
The LP fuel line connects the HP fuel pumps to the fuel delivery line from the fuel tank and lines system. A double latch quick release connector at the start of the LP fuel line connects with the fuel line from the fuel tank mounted fuel pump module. One P-clip secures the LP fuel line to the right side of the cylinder block. A heat reflective and insulation sleeve is installed on the LP fuel line where it runs behind the right exhaust manifold.
The HP fuel lines connect the HP fuel pumps to the right fuel rail and the crossover tube. Two P-clips and a pipe clamp attach the HP fuel lines to the cylinder block and the Bank 1 cylinder head respectively. An integral bracket on the front HP fuel line is attached to a stud on the front-upper right camshaft cover. A pipe cover is installed on the bottom of the front HP fuel line and acoustic covers are fitted to both HP fuel lines.
HIGH PRESSURE (HP) FUEL PUMPS
| ITEM | DESCRIPTION |
|---|---|
| 1 | Crankshaft |
| 2 | Auxiliary drive chain |
| 3 | Auxiliary shaft |
| 4 | Tappet |
| 5 | High Pressure (HP) fuel pump - No. 2 |
| 6 | Acoustic cover |
The two HP fuel pumps are identical mechanically-driven pumps installed on the right side of the oil pan body, behind the generator. An O-ring seal, seals each of the HP fuel pumps in the oil pan. The front HP fuel pump is identified as No. 1 pump; the rear HP fuel pump is identified as No. 2 pump. An acoustic cover is installed on each of the HP fuel pumps.
The HP fuel pumps are single-plunger pumps. The plunger of each pump extends through the sump body and the carrier of the auxiliary shaft. A tappet on the end each plunger is operated by a two-lobe cam on the auxiliary shaft. A spring installed on the outside of the plunger ensures the plunger and tappet remain in contact with the cam.
The auxiliary shaft is driven by the crankshaft, via the auxiliary drive chain, at engine speed. The auxiliary shaft is timed to match the pump delivery strokes with crankshaft position.
Schematic diagram - High Pressure (HP) fuel pump
| ITEM | DESCRIPTION |
|---|---|
| 1 | Pressure Relief Valve (PRV) |
| 2 | Connection to High Pressure (HP) fuel lines |
| 3 | Check valve |
| 4 | Plunger |
| 5 | Feed connection from Low Pressure (LP) fuel lines |
| 6 | Damper chamber |
| 7 | Fuel metering valve |
In addition to the plunger, each HP fuel pump contains:
- A damper chamber.
- A fuel metering valve.
- A check valve.
- A PRV (Pressure Relief Valve).
The damper absorbs pressure pulses from the LP fuel system.
The fuel metering valve regulates the output pressure from the HP fuel pump. The fuel metering valve is a normally open solenoid valve controlled by the ECM. During the inlet stroke of the plunger the fuel metering valve is de-energized, which allows LP fuel into the pumping chamber. The ECM energizes the fuel metering valve closed during the delivery stroke of the plunger, which forces the fuel in the pumping chamber through the check valve into the HP lines. By changing the closing point of the fuel metering valve, the ECM can determine the volume of fuel output during the delivery stroke, and thus the pressure in the HP side of the system.
The check valve prevents the return of HP fuel to the pumping chamber during the inlet stroke of the plunger.
The PRV protects the HP side of the system from excessive pressure if there is a failure of the fuel metering valve. If the pump delivery pressure increases to 250 bar (3625 lbf/in2 ), the PRV opens and returns fuel to the inlet side of the plunger.
FUEL RAILS AND CROSSOVER TUBE
| ITEM | DESCRIPTION |
|---|---|
| 1 | Fuel rail - Bank 2 |
| 2 | Crossover tube |
| 3 | Fuel rail - Bank 1 |
| 4 | Fuel Rail Pressure and Temperature (FRPT) sensor |
| 5 | Fuel injector (6 off) |
| 6 | Hold down spring (6 off) |
The fuel rails and crossover tube are made from stainless steel. Bolts attach each fuel rail to the related cylinder head. The crossover tube connects the front HP line to the Bank 2 fuel rail, which ensures there is equal pressure in the two fuel rails. Four P-clips attach the crossover tube to the top of the charge air cooler.
The rear of the right fuel rail incorporates a threaded boss for installation of the FRPT (Fuel Rail Pressure and Temperature) sensor.
FUEL RAIL PRESSURE AND TEMPERATURE (FRPT) SENSOR
The FRPT sensor provides the ECM with a continuous signal of fuel rail pressure via hardwired connection. The FRPT sensor is installed in the rear of the Bank 1 fuel rail. The FRPT sensor is screwed into a threaded boss in the fuel rail.
The FRPT sensor contains a steel diaphragm fitted with strain gages, which are incorporated into a Wheatstone bridge. The output from the Wheatstone bridge is processed by the ECM to determine a pressure value. The FRPT sensor contains an NTC (Negative Temperature Coefficient) sensor which allows the ECM to determine the fuel temperature.
FUEL INJECTORS
The fuel injectors spray fuel from the fuel rail directly into the combustion chambers. The fuel injectors are installed close to the center of the combustion chambers, between the inlet and exhaust valves and next to the spark plug.
The fuel injectors are a push fit in the fuel rails and the cylinder heads. On each fuel injector, an O-ring seal, seals the head of the fuel injector in the fuel rail. A Teflon ring seals the nozzle of the fuel injector in the cylinder head.
Each fuel injector contains a solenoid-operated needle valve, which opens when the solenoid winding is energized. While the needle valve is open, fuel is sprayed into the combustion chamber. The solenoid winding is connected to a power feed and a ground from the ECM, which operates the fuel injectors with a two stage power supply. Initially the ECM supplies the fuel injectors with 65 V, then once the boost current reaches 11 A the power supply is switched to battery voltage. The ECM meters the amount of fuel injected into the combustion chambers by adjusting the time that the solenoid winding is energized.
There are six holes around the tip of the nozzle through which the fuel is sprayed. Two of the holes direct fuel below the spark plug. The other four holes direct fuel evenly around the remainder of the combustion chamber.
If a fuel injector fails, the engine will suffer from unstable idle speed, poor NVH (Noise, Vibration and Harshness) and poor emissions performance.