Jeep Cherokee (XJ): Description and operation
OPERATION USE THE DRB SCAN TOOL TO REPROGRAM
THE NEW POWERTRAIN CONTROL MODULE
(PCM) WITH THE VEHICLES ORIGINAL IDENTIFICATION
NUMBER (VIN) AND THE VEHICLES
ORIGINAL MILEAGE. IF THIS STEP IS
NOT DONE, A DIAGNOSTIC TROUBLE CODE
(DTC) MAY BE SET. DESCRIPTION The fuel delivery system consists of: OPERATION Fuel is returned through the fuel pump module
and back into the fuel tank through the fuel filter/
fuel pressure regulator. A separate fuel return line
from the engine to the tank is not used.
The fuel tank assembly consists of: the fuel tank,
fuel pump module assembly, fuel pump module locknut/
gasket, and rollover valve (refer to Group 25,
Emission Control System for rollover valve information).
A fuel filler/vent tube assembly using a pressure/
vacuum, 1/4 turn fuel filler cap is used. The fuel
filler tube contains a flap door located below the fuel
fill cap.
Also to be considered part of the fuel system is the
evaporation control system. This is designed to
reduce the emission of fuel vapors into the atmosphere.
The description and function of the Evaporative
Control System is found in Group 25, Emission
Control Systems.
Both fuel filters (at bottom of fuel pump module
and within fuel pressure regulator) are designed for
extended service. They do not require normal scheduled
maintenance. Filters should only be replaced if
a diagnostic procedure indicates to do so. DESCRIPTION The fuel pump module is installed in the top of the
fuel tank (Fig. 1) or (Fig. 2). The fuel pump module
contains the following components: The fuel gauge sending unit, pick-up filter and fuel
filter/fuel pressure regulator may be serviced separately.
If the electrical fuel pump requires service,
the entire fuel pump module must be replaced.
1 - ROLLOVER VALVE
1 - FUEL GAUGE FLOAT OPERATION Refer to Fuel Pump, Fuel Filter/Fuel Pressure Regulator
and Fuel Gauge Sending Unit. DESCRIPTION The fuel pump is located inside of the fuel pump
module. A 12 volt, permanent magnet, electric motor
powers the fuel pump. OPERATION Voltage to operate the electric pump is supplied
through the fuel pump relay.
Fuel is drawn in through a filter at the bottom of
the module and pushed through the electric motor
gearset to the pump outlet.
Check Valve Operation: The pump outlet contains
a one-way check valve to prevent fuel flow back
into the tank and to maintain fuel supply line pressure
(engine warm) when pump is not operational. It
is also used to keep the fuel supply line full of gasoline
when pump is not operational. After the vehicle
has cooled down, fuel pressure may drop to 0 psi
(cold fluid contracts), but liquid gasoline will remain
in fuel supply line between the check valve and fuel
injectors. Fuel pressure that has dropped to 0
psi on a cooled down vehicle (engine off) is a
normal condition. Refer to the Fuel Pressure Leak
Down Test for more information. DESCRIPTION The fuel gauge sending unit (fuel level sensor) is
attached to the side of the fuel pump module. The
sending unit consists of a float, an arm, and a variable
resistor track (card). OPERATION The fuel pump module has 4 different circuits
(wires). Two of these circuits are used for the fuel
gauge sending unit for fuel gauge operation, and for
certain OBD II emission requirements. The other 2
wires are used for electric fuel pump operation.
For Fuel Gauge Operation: A constant input
voltage source of about 12 volts (battery voltage) is
supplied to the resistor track on the fuel gauge sending
unit. This is fed directly from the Powertrain
Control Module (PCM). NOTE: For diagnostic purposes,
this 12V power source can only be verified
with the circuit opened (fuel pump module
electrical connector unplugged). With the connectors
plugged, output voltages will vary from
about.6 volts at FULL, to about 8.6 volts at
EMPTY (about 8.6 volts at EMPTY for Jeep
models, and about 7.0 volts at EMPTY for
Dodge Truck models). The resistor track is used to
vary the voltage (resistance) depending on fuel tank
float level. As fuel level increases, the float and arm
move up, which decreases voltage. As fuel level
decreases, the float and arm move down, which
increases voltage. The varied voltage signal is
returned back to the PCM through the sensor return
circuit.
Both of the electrical circuits between the fuel
gauge sending unit and the PCM are hard-wired (not
multi-plexed). After the voltage signal is sent from
the resistor track, and back to the PCM, the PCM
will interpret the resistance (voltage) data and send
a message across the multi-plex bus circuits to the
instrument panel cluster. Here it is translated into
the appropriate fuel gauge level reading. Refer to
Instrument Panel for additional information.
For OBD II Emission Monitor Requirements:
The PCM will monitor the voltage output sent from
the resistor track on the sending unit to indicate fuel
level. The purpose of this feature is to prevent the
OBD II system from recording/setting false misfire
and fuel system monitor diagnostic trouble codes.
The feature is activated if the fuel level in the tank
is less than approximately 15 percent of its rated
capacity. If equipped with a Leak Detection Pump
(EVAP system monitor), this feature will also be activated
if the fuel level in the tank is more than
approximately 85 percent of its rated capacity. DESCRIPTION The combination fuel filter and fuel pressure regulator
is located on the top of fuel pump module (Fig.
1).
OPERATION A combination fuel filter and fuel pressure regulator
is used on all engines. A separate frame mounted
fuel filter is not used with any engine.
Fuel Pressure Regulator Operation: The pressure
regulator is a mechanical device that is not controlled
by engine vacuum or the Powertrain Control
Module (PCM).
The regulator is calibrated to maintain fuel system
operating pressure of approximately 339 kPa 6 34
kPa (49.2 psi 6 5 psi) at the fuel injectors. It contains
a diaphragm, calibrated springs and a fuel
return valve. The internal fuel filter is also part of
the assembly.
Fuel is supplied to the filter/regulator by the electric
fuel pump through an opening tube at the bottom
of filter/regulator (Fig. 3).
The regulator acts as a check valve to maintain
some fuel pressure when the engine is not operating.
This will help to start the engine. A second check
valve is located at the outlet end of the electric fuel
pump. Refer to Fuel Pump-Description and Operation for more information. Also
refer to
the Fuel Pressure Leak Down Test and the Fuel
Pump Pressure Tests.
If fuel pressure at the pressure regulator exceeds
approximately 49 psi, an internal diaphragm closes
and excess fuel is routed back into the tank through
the pressure regulator. A separate fuel return line is
not used.
1 - FUEL FILTER/FUEL PRESSURE REGULATOR DESCRIPTION The fuel tank is constructed of a plastic material.
Its main functions are for fuel storage and for placement
of the fuel pump module. OPERATION All models pass a full 360 degree rollover test
without fuel leakage. To accomplish this, fuel and
vapor flow controls are required for all fuel tank connections.
A rollover valve(s) is mounted into the top of the
fuel tank (or pump module). Refer to Emission Control
System for rollover valve information.
An evaporation control system is connected to the
rollover valve(s) to reduce emissions of fuel vapors
into the atmosphere. When fuel evaporates from the
fuel tank, vapors pass through vent hoses or tubes to
a charcoal canister where they are temporarily held.
When the engine is running, the vapors are drawn
into the intake manifold. Certain models are also
equipped with a self-diagnosing system using a Leak
Detection Pump (LDP). Refer to Emission Control
System for additional information. DESCRIPTION An individual fuel injector (Fig. 4) is used for each
individual cylinder.
1 - FUEL INJECTOR OPERATION The top (fuel entry) end of the injector (Fig. 4) is
attached into an opening on the fuel rail.
The fuel injectors are electrical solenoids. The
injector contains a pintle that closes off an orifice at
the nozzle end. When electric current is supplied to
the injector, the armature and needle move a short
distance against a spring, allowing fuel to flow out
the orifice. Because the fuel is under high pressure, a
fine spray is developed in the shape of a pencil
stream. The spraying action atomizes the fuel, adding
it to the air entering the combustion chamber.
The nozzle (outlet) ends of the injectors are positioned
into openings in the intake manifold just
above the intake valve ports of the cylinder head.
The engine wiring harness connector for each fuel
injector is equipped with an attached numerical tag
(INJ 1, INJ 2 etc.). This is used to identify each fuel
injector.
The injectors are energized individually in a
sequential order by the powertrain control module
(PCM). The PCM will adjust injector pulse width by
switching the ground path to each individual injector
on and off. Injector pulse width is the period of time
that the injector is energized. The PCM will adjust injector pulse width based
on various inputs it
receives.
Battery voltage is supplied to the injectors through
the ASD relay.
The PCM determines injector pulse width based on
various inputs. DESCRIPTION The fuel injector rail is used to mount the fuel
injectors to the engine (Fig. 5). On the 2.5L 4-cylinder
engine, a fuel damper is located at the front of
the fuel rail (Fig. 5).
1 - FUEL DAMPER OPERATION The fuel injector rail supplies the necessary fuel to
each individual fuel injector.
The fuel damper is used only to help control fuel
pressure pulsations. These pulsations are the result
of the firing of the fuel injectors. It is not used as a
fuel pressure regulator. The fuel pressure regulator is
not mounted to the fuel rail on any engine. It is
located on the fuel tank mounted fuel pump module.
Refer to Fuel Filter/Fuel Pressure Regulator in this
group for information.
The fuel rail is not repairable. DESCRIPTION The fuel rail is mounted to the intake manifold
(Fig. 6). It is used to mount the fuel injectors to the
engine. On the 4.0L 6-cylinder engine, a fuel
damper is located near the center of the fuel rail
(Fig. 6).
1 - INJ. #1 OPERATION The fuel injector rail supplies the necessary fuel to
each individual fuel injector.
The fuel damper is used only to help control fuel
pressure pulsations. These pulsations are the result
of the firing of the fuel injectors. It is not used as a
fuel pressure regulator. The fuel pressure regulator is
not mounted to the fuel rail on any engine. It is
located on the fuel tank mounted fuel pump module Refer to Fuel Filter/Fuel
Pressure Regulator in this
group for information.
The fuel rail is not repairable. DESCRIPTION The plastic fuel tank filler tube cap is threaded
onto the end of the fuel fill tube. Certain models are
equipped with a 1/4 turn cap. OPERATION The loss of any fuel or vapor out of fuel filler tube
is prevented by the use of a pressure-vacuum fuel fill
cap. Relief valves inside the cap will release fuel tank
pressure at predetermined pressures. Fuel tank vacuum
will also be released at predetermined values.
This cap must be replaced by a similar unit if
replacement is necessary. This is in order for the system
to remain effective.
CAUTION: Remove fill cap before servicing any fuel
system component to relieve tank pressure. If
equipped with a California emissions package and a
Leak Detection Pump (LDP), the cap must be tightened
securely. If cap is left loose, a Diagnostic
Trouble Code (DTC) may be set. DESCRIPTION Also refer to Quick-Connect Fittings. WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT
PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING ANY FUEL SYSTEM HOSES,
FITTINGS OR LINES, THE FUEL SYSTEM PRESSURE
MUST BE RELEASED. REFER TO THE FUEL
SYSTEM PRESSURE RELEASE PROCEDURE IN
THIS GROUP.
The lines/tubes/hoses used on fuel injected vehicles
are of a special construction. This is due to the
higher fuel pressures and the possibility of contaminated
fuel in this system. If it is necessary to replace
these lines/tubes/hoses, only those marked EFM/EFI
may be used.
If equipped: The hose clamps used to secure rubber
hoses on fuel injected vehicles are of a special
rolled edge construction. This construction is used to
prevent the edge of the clamp from cutting into the
hose. Only these rolled edge type clamps may be
used in this system. All other types of clamps may
cut into the hoses and cause high-pressure fuel leaks.
Use new original equipment type hose clamps. DESCRIPTION Different types of quick-connect fittings are used to
attach various fuel system components, lines and
tubes. These are: a single-tab type, a two-tab type or
a plastic retainer ring type. Some are equipped with
safety latch clips. Some may require the use of a special
tool for disconnection and removal. Refer to
Quick-Connect Fittings Removal/Installation for more
information. CAUTION: The interior components (o-rings, clips)
of quick-connect fittings are not serviced separately,
but new plastic spacers are available for
some types. If service parts are not available, do
not attempt to repair the damaged fitting or fuel line
(tube). If repair is necessary, replace the complete
fuel line (tube) assembly.PCM vin reprogramming
Fuel delivery system
Fuel pump module
Fig. 1 Fuel Tank/Fuel Pump Module (Top View)
2 - RETAINER CLAMP
3 - LOCKNUT
4 - FUEL PUMP MODULE
5 - FUEL FILTER/FUEL PRESSURE REGULATOR
6 - ALIGNMENT ARROW
7 - PIGTAIL HARNESS
8 - FUEL SUPPLY TUBE
9 - EVAP CANISTER VENT LINE
Fig. 2 Fuel Pump Module Components
2 - PICK-UP FILTER
3 - FUEL GAUGE SENDING UNIT
4 - FUEL FILTER/FUEL PRESSURE REGULATOR
5 - ELECTRIC FUEL PUMP
6 - PIGTAIL WIRING HARNESSFuel pump
Fuel gauge sending unit
Fuel filter/fuel pressure regulator
Fig. 3 Fuel Filter/Fuel Pressure Regulator
2 - TO FUEL INJECTORS
3 - FUEL SUPPLY TUBE
4 - O-RINGS
5 - FUEL INLET FROM PUMP
6 - FUEL RETURN TO TANKFuel tank
Fuel injectors
Fig. 4 Fuel Injector-Typical
2 - NOZZLE
3 - TOP (FUEL ENTRY)Fuel injector rail/fuel damper-2.5L
engine
Fig. 5 Fuel Injector Rail/Fuel Damper-2.5L Engine
2 - FUEL INJECTOR
3 - NUMBERED TAG
4 - FUEL RAIL
5 - FUEL RAIL MOUNTING BOLTS/NUTS
6 - TEST PORT
7 - CABLE BRACKETFuel rail/fuel damper-4.0L engine
Fig. 6 Fuel Rail/Fuel Damper-4.0L Engine
2 - INJ. #2
3 - INJ. #3
4 - INJ. #4
5 - INJ. #5
6 - INJ. #6
7 - FUEL INJECTOR RAIL
8 - FUEL DAMPER
9 - PRESSURE TEST PORT CAP
10 - MOUNTING BOLTS (4)
11 - QUICK-CONNECT FITTINGFuel tank filler tube cap
Fuel tubes/lines/hoses and clamps
Quick-connect fittings
Other materials:
Output shaft rear bearing. Governor and park gear. Park lock
Output shaft rear bearing
REMOVAL
(1) Remove extension housing.
(2) Remove snap ring that retains rear bearing on
output shaft (Fig. 84).
(3) Remove bearing from output shaft.
INSTALLATION
(1) Install bearing on output shaft. Be sure retaining
ring groove in outer circumference of bearing ...