Pontiac Fiero 1988 Service Manual page 666

DRIVEABILITY AND EMISSIONS - FUEL INJECTION (PORT) 6E3-C2-1
SECTION C2
FUEL CONTROL SYSTEI
CONTENTS
G E N E R A L D E S C R I P T I O N . . . C2-1
PURPOSE
. . « « . . * * . . . . * * » o e « .
. . « . * . C2"
1
MODES OF OPERATION . . . . . . . . . C2-1
Starting M o d e C2-1
Clear Flood M o d e . . . . C2-2
Run Mode C2-2
Acceleration M o d e . . . . . . . . . C2-2
Deceleration M o d e C2-3
Battery Voltage Correction Mode . . . . . C2-3
Fuel Cutoff M o d e . . . . . . . . . . . . . . . . . C2-3
F U E L C O N T R O L S Y S T E M C O M P O N E N T S C2-3
BASIC SYSTEM OPERATION . . . . C2-3
FUEL RAIL ASSEMBLY . C2-4
Fuel Injector Assembly . . . . . C2-4
Pressure Regulator Assembly . . . . . . . . C2-4
THROTTLE BODY ASSEMBLY C2-5
Idle Air Control (IAC) Valve Assembly . . C2-5
Throttle Position Sensor (TPS) . . . . . . . . C2-5
FUEL PUMP C2-6
FUEL PUMP ELECTRICAL C I R C U I T . . . . . . . . C2-6
GENERAL DESCRIPTION
PURPOSE
The basic function of the fuel control system is to
control fuel delivery to the engine.
Fuel is delivered to the engine by individual fuel
injectors mounted in the intake manifold, near each
cylinder.
The main control sensor is the oxygen (O2) sensor,
which is located in the exhaust manifold. The Oo
sensor tells the engine control module (ECM) how
much oxygen is in the exhaust gas, and the ECM
changes the air/fuel ratio to the engine by controlling
the fuel injectors. The best mixture to minimize
exhaust emissions is 14.7 to 1, which allows the
catalytic converter to operate most efficiently.
Because of the constant measuring and adjusting of
the air/fuel ratio, the fuel injection system is called a
"Closed Loop" System (shown in Figure C2-1).
MODES OF OPERATION
The ECM looks at voltages from several sensors to
determine how much fuel to give the engine. The fuel
is delivered under one of several conditions, called
"modes." All the modes are controlled by the ECM,
and are described below.
D I A G N O S I S C 2 - 6
FUEL CONTROL SYSTEM C 2 - 6
IDLE AIR CONTROL VALVE C2-7
FUEL SYSTEM PRESSU RE TEST . . . . . . . . . C2-7
ON-VEH1CLE SERVICE C2-7
PORT FUEL INJECTION COMPONENTS C 2 - 7
FUEL PRESSURE RELIEF PROCEDURE . . . . . C2-7
P L E N U M . . C2-7
FUEL RAIL ASSEMBLY . . . . . . . . . . . . C2-8
COLD START VALVE A S S E M B L Y . . . . . . . . . C 2 - 1 0
FUEL PRESSURE CONNECTION ASSEMBLY . C2-10
FUEL BLOCK ASSEMBLY . . . . . . . . . . . . . . C2-11
PORT FUEL INJECTOR C2-11
PRESSURE REGULATOR ASSEMBLY . . . . . . C2-12
COLD START FUEL INJECTION SWITCH . . . C 2 - 1 2
THROTTLE BODY A S S E M B L Y . . . . . . . . . . . C2-12
IDLE AIR CONTROL VALVE . . . . . . . . . . . . C2-13
FUEL PUMP RELAY . . . . . . . . . . . . . . . . . . C2-14
PARTS INFORMATION C 2 - 1 4
[7] ENGINE CONTROL MODULE (ECM)
[7] FUEL INJECTORS
EXHAUST O X Y G E N 0
2
SENSOR
CATALYTIC CONVERTER
8P 0337-SYE
1 15 87
Figure C2-1 - "Closed L o o p " System
Starting Mode
When the ignition is first turned "ON," the ECM
turns "ON" the fuel pump relay for two seconds, and
the fuel pump builds up fuel pressure. The ECM also
checks the coolant temperature sensor, the throttle
position sensor (TPS) and the manifold absolute
pressure (MAP) sensor, to determine the proper
air/fuel ratio for starting.