Content .. 956 957 958 959 ..

Jeep Liberty KJ. Manual - part 958

6. Connect fuel rail fuel return line at fuel rail.

7. Connect fuel pressure sensor electrical connector.

8. Install engine cover and bracket assembly (Refer to 9 - ENGINE COVER - INSTALLATION).

9. Connect negative battery cable.

14 - 52

FUEL DELIVERY - 2.8L DIESEL

FUEL LINES

DESCRIPTION

LOW-PRESSURE FUEL LINES

All fuel lines up to the fuel injection pump are considered low-pressure. This includes the fuel lines from the fuel
tank to the high pressure fuel injection pump. The fuel return lines and the fuel drain lines are also considered
low-pressure lines. High-pressure lines are used between the fuel injection pump and the fuel injectors (Refer to 14
- FUEL SYSTEM - WARNING). Also refer to High-Pressure Fuel Lines Description/Operation (Refer to 14 - FUEL
SYSTEM/FUEL DELIVERY/FUEL LINES - OPERATION).

HIGH PRESSURE FUEL LINES

CAUTION: High pressure lines can not contact each other or other components. Do not attempt to repair or
weld high pressure fuel lines that are damaged. If lines are kinked or bent, they MUST be replaced. Use only
recommended lines when replacement of high pressure fuel line is necessary.

(Refer to 14 - FUEL SYSTEM - WARNING). The high-pressure fuel lines are used between the high pressure fuel
injection pump and the fuel injector rail, and between the fuel injection rail and fuel injectors. All other fuel lines are
considered low-pressure lines.

OPERATION - HIGH PRESSURE FUEL LINES

WARNING: High - pressure lines deliver diesel fuel under extreme pressure from the injection pump to the
fuel injectors. This may be as high as 1600 bar (23,200 psi.). Use extreme caution when inspecting for high
- pressure fuel leaks. Fuel under this amount of pressure can penetrate skin causing personal injury or
death. Inspect for high - pressure fuel leaks with a sheet of cardboard. Wear safety goggles and adequate
protective clothing when servicing fuel system.

CAUTION: The high-pressure fuel lines cannot contact each other or other components. Do not attempt to
weld high-pressure fuel lines or to repair lines that are damaged. If lines are ever kinked or bent, they must
be replaced. Use only the recommended lines when replacement of high-pressure fuel line is necessary.

High-pressure fuel lines deliver fuel under extremely high pressure from the high pressure pump to the fuel injectors
(Refer to 14 - FUEL SYSTEM - WARNING). The lines expand and contract from the high-pressure fuel pulses gen-
erated during the injection process. All high-pressure fuel lines are of the same length and inside diameter. Correct
high-pressure fuel line usage and installation is critical to smooth engine operation.

FUEL DELIVERY - 2.8L DIESEL

14 - 53

FUEL INJECTION PUMP

DESCRIPTION

A radial, 3 piston pump with a gear type fuel pump
attached to the back, is used as the high pressure
pump for fuel pressure generation (Refer to 14 - FUEL
SYSTEM - WARNING).

The pump is driven by the timing belt. Pressure is
generated independently of the injection process. The
pump is lubricated with diesel fuel and is not respon-
sible for fuel injection timing.

OPERATION

Cascade Overflow Valve

Instead of using an electric supply pump, this fuel system uses a gear supply pump located inside the rear of the
high pressure pump. The pump is driven by an eccentric on the end of the high pressure pump shaft. The gear
pump draws fuel from the fuel tank through the fuel filter.

The pressurized outlet side of the gear pump provides pressurized fuel to a branched circuit internal to the high
pressure pump flange, which supples both the fuel quantity solenoid and the cascade overflow valve. Because the
gear pump increases fuel flow and pressure as the engine rpm increases, the pressure is regulated by the cascade
overflow valve. The cascade overflow valve and gear supply pump are not serviced independently of the high pres-
sure pump.

The cascade overflow valve has two functions:

•

Regulation of lubrication fuel to the internal moving parts of the high pressure pump

•

Regulation of the fuel pressure being supplied to the fuel quantity solenoid

The cascade valve has a machined center piece that has three drillings. One for overflow, one for lubrication and
one for supply. The valve works in three stages based on the pressure entering the inlet of the valve.

Stage 1

When the fuel pressure entering the tip of the cascade valve is between 0 and 3 bar (44 psi), the spring force is not
overcome and fuel only flows through the center drilling. This drilling always allows fuel flow through to the pump
center ring and lubricates the pump bushings and internal moving parts. This circuit also allows air to bleed during
initial cranking and returns the air to the fuel tank. The cascade valve is only in stage one during cranking.

Stage 2

When the fuel entering the cascade valve exceeds 3 bar (44 psi), but is less than 5 bar (73 psi), the center piece
of the valve moves against the spring force aligning another passage for lubrication purposes. Stage 2 can be
reached during cranking and initial start up.

14 - 54

FUEL DELIVERY - 2.8L DIESEL

Stage 3

When fuel pressure exceeds 5 bar (73 psi), the center of the valve aligns with the overflow passage. This stage
relieves the pressure into an overflow circuit that sends the fuel back to the inlet side of the gear pump which limits
maximum fuel pressure to 5 bar (73 psi). Lubrication fuel also continues to flow though the other ports during this
stage. Excess is sent back to the fuel tank through the return circuit.

High Pressure Pumping Plungers

The fuel quantity solenoid supples three high pressure pumping chambers. The pumping chambers have one way
inlet valves that allow fuel to flow into the chambers. The valves then close during compression of the fuel and
cause the high pressure fuel to overcome a ball and angled seat outlet valve.

All three pumping chambers are tied together in one circuit internal to the pump and provide high pressure fuel up
to 1600 bar (23,000 psi) through a steel line, to the fuel rail.

The pump is driven at 1:1 engine speed and is not responsible for injection timing. The pump is only responsible for
providing high pressure fuel while the ECM controls the injection timing.

REMOVAL

1. Disconnect negative battery cable.

2. Remove engine cover and bracket (Refer to 9 -

ENGINE - REMOVAL).

3. Evacuate A/C system (Refer to 24 - HEATING &

AIR

CONDITIONING/PLUMBING

STANDARD

PROCEDURE).

4. Remove cooling fan and fan shroud.

5. Remove accessory drive belt (Refer to 7 - COOL-

ING/ACCESSORY

DRIVE/DRIVE

BELTS

REMOVAL).

6. Remove fan support assembly (Refer to 7 - COOL-

ING/ENGINE/RADIATOR FAN - REMOVAL).

7. Bring piston #1 to TDC, turn crankshaft until notch

on the crankshaft hub is at the 12 o’clock position.

8. Looking at the engine from the belt side, rotate the

crankshaft 90° clockwise.

9. Remove the intake and exhaust camshaft plugs

from the camshaft cover, to introduce the camshaft
timing pins VM.1052 Intake, and VM.1053 Exhaust
(if the engine is timed correctly, the pins can be
installed).

10. Remove timing belt outer cover (Refer to 9 - ENGINE/VALVE TIMING/TIMING BELT / CHAIN COVER(S) -

REMOVAL).

11. Using special tool VM.1055, remove high pressure injection pump sprocket retaining nut.

FUEL DELIVERY - 2.8L DIESEL

14 - 55

Content .. 956 957 958 959 ..