Dodge Ram Truck 1500-2500-3500. Manual - part 1455

FUEL FILTER/PRESSURE REGULATOR

DESCRIPTION

A combination fuel filter and fuel pressure regulator (3)
is used on all engines. It is located on the top of the
fuel pump module. A separate frame mounted fuel fil-
ter is not used with any engine.

Both fuel filters (at bottom of fuel pump module and
within

fuel

pressure

regulator)

are

designed

for

extended service. They do not require normal sched-
uled maintenance. Filters should only be replaced if a
diagnostic procedure indicates to do so.

OPERATION

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 58 ± 2 psi at the fuel injec-
tors. 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/reg-
ulator.

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.

If fuel pressure at the pressure regulator exceeds approximately 60 psi, an internal diaphragm opens and excess
fuel pressure is routed back into the tank through the bottom of pressure regulator.

Both fuel filters (at bottom of fuel pump module and within fuel pressure regulator) are designed for extended ser-
vice. They do not require normal scheduled maintenance. Filters should only be replaced if a diagnostic procedure
indicates to do so.

SENSOR - FUEL LEVEL SENDING UNIT

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 current source 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 0.6 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

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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.

REMOVAL

The fuel level sending unit (fuel level sensor) and float
assembly (7) is located on the side of the fuel pump
module.

1. Remove fuel pump module from fuel tank. Refer to

Fuel Pump Module Removal/Installation.

2. Disconnect 4–wire electrical connector (3) from fuel

pump module. Separate necessary sending unit
wiring from connector using terminal pick / removal
tool. Refer to Special Tools in 8W Wiring for tool
part numbers.

3. To remove sending unit from pump module, lift on

plastic locking tab while sliding sending unit tracks.

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INSTALLATION

1. Connect necessary wiring into electrical connectors. Connect 4–wire electrical connector to pump module.

2. Position sending unit to pump module. Slide and snap into place.

3. Install fuel pump module. Refer to Fuel Pump Module Removal/Installation.

LINES, FUEL

DESCRIPTION

Also refer to Quick-Connect Fittings.

WARNING: THE FUEL SYSTEM MAY BE UNDER A CONSTANT PRESSURE (EVEN WITH THE ENGINE OFF).
BEFORE SERVICING ANY FUEL SYSTEM HOSES, FITTINGS, LINES, OR MOST COMPONENTS, FUEL SYS-
TEM PRESSURE MUST BE RELEASED. REFER TO THE FUEL SYSTEM PRESSURE RELEASE PROCEDURE.

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.

FITTING, QUICK CONNECT

DESCRIPTION

Different types of quick-connect fittings are used to attach the various fuel system components, lines and tubes.
These are: a single-button type, a two-button type, a pinch type, 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 dis-
connection and removal. Refer to Quick-Connect Fittings Removal/Installation for more information.

CAUTION: Before separating a quick-connect fitting, pay attention to what type of fitting is being used by
referring to Quick-Connect Fitting Removal. This will prevent unnecessary fitting or fitting latch breakage.

CAUTION: The interior components (o-rings, clips) of quick-connect fittings are not serviced separately, but
new plastic spacers and latches 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.

STANDARD PROCEDURE - QUICK-CONNECT FITTINGS

DISCONNECTING

WARNING: THE FUEL SYSTEM IS UNDER A CONSTANT PRESSURE (EVEN WITH ENGINE OFF). BEFORE
SERVICING ANY FUEL SYSTEM HOSE, FITTING OR LINE, FUEL SYSTEM PRESSURE MUST BE RELEASED.
REFER TO FUEL SYSTEM PRESSURE RELEASE PROCEDURE.

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1. Perform fuel pressure release procedure. Refer to Fuel Pressure Release Procedure.

2. Disconnect negative battery cable from battery.

3. Clean fitting of any foreign material before disassembly.

4. Single–Button Type Fitting: This type of fitting is

equipped with a single push-button (2) located on
the quick-connect fitting.

5. The push-button is attached to two internal latches

(1). To disconnect, press on push-button with your
thumb and unlatch fitting from fuel line. Special
tools are not required for disconnection. DO NOT
ATTEMPT TO PRY OR PULL UP ON PUSH-BUT-
TON. LATCHES WILL BE BROKEN.

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