Fuel Gauge Sending Unit; Fuel Filter/Fuel Pressure Regulator; Fuel Pump Module Components - Jeep Wrangler 1997 Manual

14- 4 FUEL SYSTEM
DESCRIPTION AND OPERATION (Continued)
FUEL SUPPLY RETAINER FUEL FILTER/
TUBE FRONT CLAMP
FUEL PRESSURE
REGULATOR
ROLLOVER
ELECTRICAL TOP OF
VALVE CONNECTOR
FUEL TANK
80 .43851
Fig. 1 Fuel TanklFuel Pump Module (Top View)
FUEL GAUGE
FLOAT
FUEL GAUGE
FUEL FILTER/FUEL
SENDING UNIT
PRESSURE REGULATOR
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Fig. 2 Fuel Pump Module Components
FUEL GAUGE SENDING UNIT
The fuel gauge sending unit is attached to the side
of the fuel pump module (Fig. 2). The sending unit
consists of a float, an arm, and a variable resistor
(track) . The resistor track is used to send electrical
signals to the Powertrain Control Module (PCM) for
fuel gauge operation and for OBD II emission
requirements .
For fuel gauge operation: As fuel level
increases, the float and arm move up . This decreases
the sending unit resistance, causing the fuel gauge to
read full . As fuel level decreases, the float and arm
move down . This increases the sending unit resis-
tance causing the fuel gauge to read empty.
After this fuel level signal is sent to the PCM, the
PCM will transmit the data across the CCD bus cir-
cuits to the instrument panel . Here it is translated
into the appropriate fuel gauge level reading.
For OBD H emission requirements : The voltage
signal is sent from the resistor track to the PCM to
indicate fuel level . The purpose of this feature is to
prevent a false setting of misfire and fuel system
monitor trouble codes if the fuel level in the tank is
less than 15 percent of its rated capacity.
FUEL FILTER/FUEL PRESSURE REGULATOR
A combination fuel filter and fuel pressure regula-
tor is used on all engines. It is located on the top of
fuel pump module (Fig. 1). A separate frame mounted
fuel filter is not used with any engine .
Fuel Pressure Regulator Operation : The pres-
sure regulator is a mechanical device that is not con-
trolled by engine vacuum or the Powertrain Control
Module (PCM).
The regulator is calibrated to maintain fuel system
operating pressure of approximately 338 kPa (49 psi)
at the fuel injectors . It contains a diaphragm, cali-
brated springs and a fuel return valve. The internal
fuel filter is also part of the assembly .
FUEL FILTER/FUEL
PRESSURE
REGULATOR
FUEL INLET FROM PUMP
Fig. 3 Fuel Filter/Fuel Pressure Regulator
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Fuel is supplied to the filter/regulator by the elec-
tric fuel pump through an opening tube at the bot-
tom of filter/regulator (Fig. 3).
The fuel pump module contains a check valve to
maintain some fuel pressure when the engine is not
operating. This will help to start the engine.
If fuel pressure at the pressure regulator exceeds
approximately 49 psi, an internal diaphragm closes
and excess fuel pressure is routed back into the tank
through the pressure regulator . A separate fuel
return line is not used with any engine .
FUEL TANK
All models pass a full 360 degree rollover test
without fuel leakage. To accomplish this, fuel and