Chrysler neon 1997 Service Manual page 1291

14 - 4 FUEL SYSTEM
DESCRIPTION AND OPERATION (Continued)
ELECTRIC FUEL PUMP
The electric fuel pump is located in and is part of
the fuel pump module. It is a positive displacement,
gerotor type, immersible pump with a permanent
magnet electric motor. The fuel pump module is sus-
pended in fuel in the fuel tank. The pump draws fuel
through a strainer and pushes it through the motor
to the outlet. The pump contains a check valves. The
valve, in the pump outlet, maintains pump pressure
during engine off conditions. The fuel pump relay
provides voltage to the fuel pump.
The fuel pump has a maximum deadheaded pres-
sure output of approximately 880 kPa (130 psi). The
regulator adjusts fuel system pressure to approxi-
mately 338 kPa (49 psi).
FUEL GAUGE SENDING UNIT
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 vari-
able 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
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 II 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. This is if the fuel level in the
tank is less than approximately 15 percent of its
rated capacity.
FUEL FILTER/FUEL PRESSURE REGULATOR
A combination fuel filter and fuel pressure regula-
tor is used on all gas powered engines. It is located
on the top of the fuel pump module. A separate frame
mounted fuel filter is not used.
Fuel Pressure Regulator Operation: The pres-
sure regulator is a mechanical device that is cali-
brated to maintain fuel system operating pressure of
approximately 338 kPa (49 psi) at the fuel injectors.
It contains a diaphragm, calibrated springs and a
fuel return valve. The internal fuel filter (Fig. 2) is
also part of the assembly.
operation: As fuel
MET RUBBER LOCKING TAB INTERNAL FUEL FILTER CALIBRATED SPRINGS AT MODULE GROM- PUMP
Fuel is supplied to the filter/regulator by the elec-
tric fuel pump through an opening tube at the bot-
tom of filter/regulator.
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 gas powered engine.
level
Fig. 2 Side View—Filter/Regulator
FUEL TANK
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 con-
nections.
All models have a pressure relief/rollover valve
mounted on the top of the fuel pump module.
An evaporative control system is used to reduce
emissions of fuel vapors into atmosphere by evapora-
tion and to reduce unburned hydrocarbons emitted
by vehicle engine. When fuel evaporates from fuel
tank, vapors pass through vent hoses or tubes to a
charcoal canister. The vapors are temporarily held in
the canister. When the engine is running, the vapors
are drawn into intake manifold. Refer to Group 25,
Emission Control System for additional information.
FUEL RAIL
The fuel rail supplies the necessary fuel to each
individual fuel injector and is mounted to the intake
manifold (Fig. 3). The fuel pressure regulator is no
FUEL INLET O-RINGS EXCESS FUEL FLOW TO FUEL INJEC- FUEL FUEL FILTER/FUEL SURE REGULATOR BACK TANK TORS TO PRES-
PL